File uploads and webdav give me timeouts

Nextcloud config:

{
  "system": {
    "instanceid": "***REMOVED SENSITIVE VALUE***",
    "passwordsalt": "***REMOVED SENSITIVE VALUE***",
    "secret": "***REMOVED SENSITIVE VALUE***",
    "trusted_domains": [
      "192.168.0.32",
      "cloud.torbenarne.de",
      "c.toaw.de"
    ],
    "datadirectory": "***REMOVED SENSITIVE VALUE***",
    "dbtype": "mysql",
    "version": "19.0.3.1",
    "overwrite.cli.url": "https://cloud.torbenarne.de",
    "dbname": "***REMOVED SENSITIVE VALUE***",
    "dbhost": "***REMOVED SENSITIVE VALUE***",
    "dbport": "",
    "dbtableprefix": "oc_",
    "mysql.utf8mb4": true,
    "dbuser": "***REMOVED SENSITIVE VALUE***",
    "dbpassword": "***REMOVED SENSITIVE VALUE***",
    "installed": true,
    "mail_smtpmode": "smtp",
    "mail_smtpsecure": "ssl",
    "mail_sendmailmode": "smtp",
    "mail_from_address": "***REMOVED SENSITIVE VALUE***",
    "mail_domain": "***REMOVED SENSITIVE VALUE***",
    "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
    "mail_smtpauth": 1,
    "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
    "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
    "mail_smtpport": "465",
    "mail_smtpauthtype": "LOGIN",
    "maintenance": false,
    "theme": "",
    "loglevel": 2,
    "updater.release.channel": "stable",
    "log_query": false,
    "memcache.local": "\\OC\\Memcache\\APCu",
    "memcache.distributed": "\\OC\\Memcache\\Redis",
    "memcache.locking": "\\OC\\Memcache\\Redis",
    "redis": {
      "host": "***REMOVED SENSITIVE VALUE***",
      "port": 0,
      "dbindex": 0
    },
    "ldapIgnoreNamingRules": false,
    "ldapProviderFactory": "OCA\\User_LDAP\\LDAPProviderFactory",
    "updater.secret": "***REMOVED SENSITIVE VALUE***"
  },
  "apps": {
    "accessibility": {
      "enabled": "yes",
      "installed_version": "1.5.0",
      "types": ""
    },
    "activity": {
      "enabled": "yes",
      "installed_version": "2.12.0",
      "notify_email_calendar": "0",
      "notify_email_calendar_event": "0",
      "notify_email_calendar_todo": "0",
      "notify_email_comments": "0",
      "notify_email_favorite": "0",
      "notify_email_file_changed": "0",
      "notify_email_file_created": "0",
      "notify_email_file_deleted": "1",
      "notify_email_file_restored": "0",
      "notify_email_phonetrack": "0",
      "notify_email_phonetrack_geofence_event": "1",
      "notify_email_phonetrack_proximity_event": "1",
      "notify_email_public_links": "0",
      "notify_email_remote_share": "1",
      "notify_email_shared": "0",
      "notify_email_spreed": "0",
      "notify_email_systemtags": "0",
      "notify_setting_batchtime": "86400",
      "notify_setting_self": "1",
      "notify_setting_selfemail": "0",
      "notify_stream_calendar": "1",
      "notify_stream_calendar_event": "1",
      "notify_stream_calendar_todo": "1",
      "notify_stream_comments": "1",
      "notify_stream_favorite": "1",
      "notify_stream_file_changed": "1",
      "notify_stream_file_created": "1",
      "notify_stream_file_deleted": "1",
      "notify_stream_file_favorite": "1",
      "notify_stream_file_restored": "1",
      "notify_stream_phonetrack": "1",
      "notify_stream_phonetrack_geofence_event": "1",
      "notify_stream_phonetrack_proximity_event": "1",
      "notify_stream_public_links": "1",
      "notify_stream_remote_share": "1",
      "notify_stream_shared": "1",
      "notify_stream_spreed": "1",
      "notify_stream_systemtags": "1",
      "types": "filesystem"
    },
    "admin_audit": {
      "enabled": "yes",
      "installed_version": "1.9.0",
      "types": "logging"
    },
    "backgroundjob": {
      "lastjob": "2813"
    },
    "calendar": {
      "enabled": "yes",
      "installed_version": "2.0.4",
      "types": ""
    },
    "cloud_federation_api": {
      "enabled": "yes",
      "installed_version": "1.2.0",
      "types": "filesystem"
    },
    "comments": {
      "enabled": "yes",
      "installed_version": "1.9.0",
      "types": "logging"
    },
    "contacts": {
      "enabled": "yes",
      "installed_version": "3.3.0",
      "types": ""
    },
    "contactsinteraction": {
      "enabled": "yes",
      "installed_version": "1.0.0",
      "types": "dav"
    },
    "core": {
      "backgroundjobs_mode": "cron",
      "default_encryption_module": "OC_DEFAULT_MODULE",
      "encryption_enabled": "no",
      "enterpriseLogoChecked": "yes",
      "installedat": "1548175056.2271",
      "lastcron": "1599857523",
      "lastupdateResult": "[]",
      "lastupdatedat": "1599854282",
      "oc.integritycheck.checker": "[]",
      "public_files": "files_sharing/public.php",
      "public_webdav": "dav/appinfo/v1/publicwebdav.php",
      "scss.variables": "17b205f953aa78b22c6907423017e63c",
      "shareapi_allow_share_dialog_user_enumeration": "no",
      "shareapi_default_expire_date": "yes",
      "shareapi_default_internal_expire_date": "yes",
      "shareapi_enable_link_password_by_default": "yes",
      "shareapi_enforce_expire_date": "yes",
      "shareapi_internal_enforce_expire_date": "yes",
      "shareapi_public_link_disclaimertext": "Diese Datei wurde von einem Nutzer dieser Cloud hochgeladen und wird nicht vom Administrator manuell oder automatisch kontrolliert. Falls ein Verstoß gegen geltendes Recht vorliegen sollte, bitte sofort der Administration melden (abuse@torbenarne.de).",
      "theming.variables": "3637626259538892dd7d580e6d7daaba",
      "updater.secret.created": "1599771267",
      "vendor": "nextcloud"
    },
    "dav": {
      "buildCalendarReminderIndex": "yes",
      "buildCalendarSearchIndex": "yes",
      "chunks_migrated": "1",
      "enabled": "yes",
      "installed_version": "1.15.0",
      "regeneratedBirthdayCalendarsForYearFix": "yes",
      "types": "filesystem"
    },
    "deck": {
      "enabled": "yes",
      "installed_version": "1.0.5",
      "types": "dav"
    },
    "documentserver_community": {
      "enabled": "yes",
      "installed_version": "0.1.7",
      "types": "filesystem"
    },
    "encryption": {
      "enabled": "yes",
      "encryptHomeStorage": "0",
      "installed_version": "2.7.0",
      "masterKeyId": "master_c0d6894c",
      "publicShareKeyId": "pubShare_c0d6894c",
      "recoveryKeyId": "recoveryKey_c0d6894c",
      "types": "filesystem"
    },
    "end_to_end_encryption": {
      "enabled": "yes",
      "installed_version": "1.5.2",
      "types": "dav,filesystem"
    },
    "federatedfilesharing": {
      "enabled": "yes",
      "installed_version": "1.9.0",
      "types": ""
    },
    "federation": {
      "autoAddServers": "1",
      "enabled": "yes",
      "installed_version": "1.9.0",
      "types": "authentication"
    },
    "files": {
      "cronjob_scan_files": "500",
      "default_quota": "10 GB",
      "enabled": "yes",
      "installed_version": "1.14.0",
      "types": "filesystem",
      "watermark_allGroups": "no",
      "watermark_allGroupsList": "",
      "watermark_allTags": "no",
      "watermark_allTagsList": "",
      "watermark_enabled": "yes",
      "watermark_linkAll": "yes",
      "watermark_linkRead": "no",
      "watermark_linkSecure": "no",
      "watermark_linkTags": "no",
      "watermark_linkTagsList": "",
      "watermark_shareAll": "yes",
      "watermark_shareRead": "no",
      "watermark_text": "toaw.de"
    },
    "files_accesscontrol": {
      "enabled": "yes",
      "installed_version": "1.9.1",
      "types": "filesystem"
    },
    "files_antivirus": {
      "av_path": "/usr/bin/clamscan",
      "enabled": "yes",
      "installed_version": "3.0.0",
      "types": "filesystem,dav"
    },
    "files_automatedtagging": {
      "enabled": "yes",
      "installed_version": "1.9.0",
      "types": "filesystem"
    },
    "files_external": {
      "enabled": "yes",
      "installed_version": "1.10.0",
      "types": "filesystem"
    },
    "files_markdown": {
      "enabled": "yes",
      "installed_version": "2.3.0",
      "types": ""
    },
    "files_mindmap": {
      "enabled": "yes",
      "installed_version": "0.0.22",
      "types": ""
    },
    "files_pdfviewer": {
      "enabled": "yes",
      "installed_version": "1.8.0",
      "types": ""
    },
    "files_readmemd": {
      "auto_refresh": "false",
      "enabled": "no",
      "fileslist_footer": "[\"README\"]",
      "fileslist_header": "[\"HEADER\"]",
      "installed_version": "1.1.4",
      "show_asciidoc": "false",
      "show_html": "false",
      "show_title": "true",
      "types": "filesystem",
      "yellow_back": "true"
    },
    "files_rightclick": {
      "enabled": "yes",
      "installed_version": "0.16.0",
      "types": ""
    },
    "files_sharing": {
      "enabled": "yes",
      "incoming_server2server_group_share_enabled": "yes",
      "installed_version": "1.11.0",
      "lookupServerEnabled": "yes",
      "outgoing_server2server_group_share_enabled": "yes",
      "types": "filesystem"
    },
    "files_texteditor": {
      "enabled": "no",
      "installed_version": "2.8.0",
      "types": ""
    },
    "files_trashbin": {
      "enabled": "yes",
      "installed_version": "1.9.0",
      "types": "filesystem,dav"
    },
    "files_versions": {
      "enabled": "yes",
      "installed_version": "1.12.0",
      "types": "filesystem,dav"
    },
    "files_videoplayer": {
      "enabled": "yes",
      "installed_version": "1.8.0",
      "types": ""
    },
    "firstrunwizard": {
      "enabled": "yes",
      "installed_version": "2.8.0",
      "types": "logging"
    },
    "flowupload": {
      "enabled": "yes",
      "installed_version": "1.0.0",
      "types": ""
    },
    "gallery": {
      "enabled": "no",
      "installed_version": "18.4.0",
      "types": ""
    },
    "groupfolders": {
      "enabled": "yes",
      "installed_version": "7.0.0",
      "types": "filesystem,dav"
    },
    "keeweb": {
      "enabled": "no",
      "installed_version": "0.6.2",
      "types": "filesystem"
    },
    "logreader": {
      "enabled": "yes",
      "installed_version": "2.4.0",
      "relativedates": "1",
      "types": ""
    },
    "lookup_server_connector": {
      "enabled": "yes",
      "installed_version": "1.7.0",
      "types": "authentication"
    },
    "mail": {
      "enabled": "yes",
      "installed_version": "1.4.1",
      "types": ""
    },
    "news": {
      "enabled": "yes",
      "installed_version": "14.2.2",
      "types": ""
    },
    "nextcloud_announcements": {
      "enabled": "yes",
      "installed_version": "1.8.0",
      "pub_date": "Thu, 24 Oct 2019 00:00:00 +0200",
      "types": "logging"
    },
    "notes": {
      "enabled": "yes",
      "installed_version": "3.6.4",
      "types": ""
    },
    "notifications": {
      "enabled": "yes",
      "installed_version": "2.7.0",
      "types": "logging"
    },
    "oauth2": {
      "enabled": "yes",
      "installed_version": "1.7.0",
      "types": "authentication"
    },
    "onlyoffice": {
      "enabled": "no",
      "installed_version": "2.1.2",
      "skey": "1548230277817",
      "types": "filesystem"
    },
    "password_policy": {
      "enabled": "yes",
      "enforceHaveIBeenPwned": "1",
      "enforceNumericCharacters": "1",
      "enforceUpperLowerCase": "1",
      "historySize": "0",
      "installed_version": "1.9.1",
      "types": "authentication"
    },
    "passwords": {
      "SSEv1ServerKey": "***REMOVED SENSITIVE VALUE***",
      "backups/moved": "yes",
      "enabled": "yes",
      "entity/purge/timeout": "31536000",
      "installed_version": "2020.9.0",
      "legacy_api_checkpoint": "1599680042",
      "legacy_api_enabled": "",
      "migration/customFields": "2020.2.0",
      "passwords/localdb/type": "hibp",
      "passwords/localdb/version": "1",
      "service/favicon": "ddg",
      "service/preview": "pageres",
      "service/security": "hibp",
      "service/words": "random",
      "settings/mail/shares": "1",
      "survey/server/mode": "2",
      "survey/server/week": "37",
      "types": "",
      "users/deleted": "[]"
    },
    "phonetrack": {
      "enabled": "yes",
      "installed_version": "0.6.4",
      "types": ""
    },
    "photos": {
      "enabled": "yes",
      "installed_version": "1.1.0",
      "types": ""
    },
    "piwik": {
      "enabled": "yes",
      "installed_version": "0.6.0",
      "siteId": "2",
      "trackDir": "true",
      "trackUser": "true",
      "types": "",
      "url": "https://home.torbenarne.de/api/v1/analytics/"
    },
    "privacy": {
      "enabled": "yes",
      "fullDiskEncryptionEnabled": "0",
      "installed_version": "1.3.0",
      "readableLocation": "de",
      "types": ""
    },
    "provisioning_api": {
      "enabled": "yes",
      "installed_version": "1.9.0",
      "types": "prevent_group_restriction"
    },
    "quota_warning": {
      "alert_email": "yes",
      "enabled": "yes",
      "installed_version": "1.8.0",
      "types": "filesystem"
    },
    "recommendations": {
      "enabled": "yes",
      "installed_version": "0.7.0",
      "types": ""
    },
    "richdocuments": {
      "canonical_webroot": "",
      "disable_certificate_verification": "",
      "enabled": "yes",
      "installed_version": "3.7.4",
      "public_wopi_url": "https://colla.c.toaw.de",
      "types": "filesystem,dav,prevent_group_restriction",
      "wopi_url": "https://cloud.torbenarne.de/apps/richdocumentscode/proxy.php?req="
    },
    "richdocumentscode": {
      "enabled": "yes",
      "installed_version": "4.2.800",
      "types": ""
    },
    "serverinfo": {
      "enabled": "yes",
      "installed_version": "1.9.0",
      "types": ""
    },
    "settings": {
      "enabled": "yes",
      "installed_version": "1.1.0",
      "types": ""
    },
    "sharebymail": {
      "enabled": "yes",
      "installed_version": "1.9.0",
      "sendpasswordmail": "no",
      "types": "filesystem"
    },
    "spreed": {
      "conversations_files": "1",
      "conversations_files_public_shares": "1",
      "enabled": "yes",
      "has_reference_id": "yes",
      "installed_version": "9.0.3",
      "project_access_invalidated": "1",
      "signaling_ticket_secret": "***REMOVED SENSITIVE VALUE***",
      "start_calls": "1",
      "stun_servers": "***REMOVED SENSITIVE VALUE***",
      "turn_servers": "***REMOVED SENSITIVE VALUE***",
      "types": "prevent_group_restriction"
    },
    "support": {
      "SwitchUpdaterServerHasRun": "yes",
      "enabled": "yes",
      "installed_version": "1.2.1",
      "types": "session"
    },
    "survey_client": {
      "apps": "yes",
      "database": "yes",
      "enabled": "yes",
      "encryption": "yes",
      "files_sharing": "yes",
      "installed_version": "1.7.0",
      "last_report": "{\"id\":\"ocua81y1ulx6\",\"items\":[[\"server\",\"version\",\"18.0.7.1\"],[\"server\",\"code\",\"other\"],[\"server\",\"enable_avatars\",\"yes\"],[\"server\",\"enable_previews\",\"yes\"],[\"server\",\"memcache.local\",\"none\"],[\"server\",\"memcache.distributed\",\"none\"],[\"server\",\"asset-pipeline.enabled\",\"no\"],[\"server\",\"filelocking.enabled\",\"yes\"],[\"server\",\"memcache.locking\",\"none\"],[\"server\",\"debug\",\"no\"],[\"server\",\"cron\",\"cron\"],[\"php\",\"version\",\"7.4.9\"],[\"php\",\"memory_limit\",-1],[\"php\",\"max_execution_time\",0],[\"php\",\"upload_max_filesize\",2097152],[\"database\",\"type\",\"mysql\"],[\"database\",\"version\",\"10.3.24\"],[\"database\",\"size\",35061760],[\"apps\",\"accessibility\",\"1.4.0\"],[\"apps\",\"activity\",\"2.11.0\"],[\"apps\",\"admin_audit\",\"1.8.0\"],[\"apps\",\"calendar\",\"2.0.3\"],[\"apps\",\"cloud_federation_api\",\"1.1.0\"],[\"apps\",\"comments\",\"1.8.0\"],[\"apps\",\"contacts\",\"3.3.0\"],[\"apps\",\"dav\",\"1.14.0\"],[\"apps\",\"documentserver_community\",\"0.1.7\"],[\"apps\",\"encryption\",\"2.6.0\"],[\"apps\",\"end_to_end_encryption\",\"1.4.0\"],[\"apps\",\"federatedfilesharing\",\"1.8.0\"],[\"apps\",\"federation\",\"1.8.0\"],[\"apps\",\"files\",\"1.13.1\"],[\"apps\",\"files_antivirus\",\"2.4.1\"],[\"apps\",\"files_external\",\"1.9.0\"],[\"apps\",\"files_markdown\",\"2.3.0\"],[\"apps\",\"files_mindmap\",\"0.0.22\"],[\"apps\",\"files_pdfviewer\",\"1.7.0\"],[\"apps\",\"files_readmemd\",\"1.1.4\"],[\"apps\",\"files_rightclick\",\"0.15.2\"],[\"apps\",\"files_sharing\",\"1.10.1\"],[\"apps\",\"files_texteditor\",\"disabled\"],[\"apps\",\"files_trashbin\",\"1.8.0\"],[\"apps\",\"files_versions\",\"1.11.0\"],[\"apps\",\"files_videoplayer\",\"1.7.0\"],[\"apps\",\"firstrunwizard\",\"2.7.0\"],[\"apps\",\"flowupload\",\"1.0.0\"],[\"apps\",\"gallery\",\"disabled\"],[\"apps\",\"groupfolders\",\"6.0.6\"],[\"apps\",\"keeweb\",\"0.6.2\"],[\"apps\",\"logreader\",\"2.3.0\"],[\"apps\",\"lookup_server_connector\",\"1.6.0\"],[\"apps\",\"mail\",\"1.4.1\"],[\"apps\",\"news\",\"14.1.11\"],[\"apps\",\"nextcloud_announcements\",\"1.7.0\"],[\"apps\",\"notes\",\"3.6.0\"],[\"apps\",\"notifications\",\"2.6.0\"],[\"apps\",\"oauth2\",\"1.6.0\"],[\"apps\",\"onlyoffice\",\"disabled\"],[\"apps\",\"password_policy\",\"1.8.0\"],[\"apps\",\"passwords\",\"2020.7.0\"],[\"apps\",\"phonetrack\",\"0.6.4\"],[\"apps\",\"photos\",\"1.0.0\"],[\"apps\",\"piwik\",\"0.5.4\"],[\"apps\",\"privacy\",\"1.2.0\"],[\"apps\",\"provisioning_api\",\"1.8.0\"],[\"apps\",\"quota_warning\",\"1.7.0\"],[\"apps\",\"recommendations\",\"0.6.0\"],[\"apps\",\"serverinfo\",\"1.8.0\"],[\"apps\",\"settings\",\"1.0.0\"],[\"apps\",\"sharebymail\",\"1.8.0\"],[\"apps\",\"spreed\",\"8.0.9\"],[\"apps\",\"support\",\"1.1.1\"],[\"apps\",\"survey_client\",\"1.6.0\"],[\"apps\",\"suspicious_login\",\"3.1.0\"],[\"apps\",\"systemtags\",\"1.8.0\"],[\"apps\",\"tasks\",\"0.13.2\"],[\"apps\",\"text\",\"2.0.0\"],[\"apps\",\"theming\",\"1.9.0\"],[\"apps\",\"twofactor_backupcodes\",\"1.7.0\"],[\"apps\",\"updatenotification\",\"1.8.0\"],[\"apps\",\"uploaddetails\",\"disabled\"],[\"apps\",\"user_usage_report\",\"1.2.3\"],[\"apps\",\"viewer\",\"1.2.0\"],[\"apps\",\"workflowengine\",\"2.0.0\"],[\"stats\",\"num_files\",23168],[\"stats\",\"num_users\",6],[\"stats\",\"num_storages\",8],[\"stats\",\"num_storages_local\",1],[\"stats\",\"num_storages_home\",7],[\"stats\",\"num_storages_other\",0],[\"stats\",\"num_comments\",94],[\"stats\",\"num_comment_markers\",2],[\"stats\",\"num_systemtags\",0],[\"stats\",\"num_systemtags_mappings\",0],[\"files_sharing\",\"num_shares\",0],[\"files_sharing\",\"num_shares_user\",0],[\"files_sharing\",\"num_shares_groups\",0],[\"files_sharing\",\"num_shares_link\",0],[\"files_sharing\",\"num_shares_link_no_password\",0],[\"files_sharing\",\"num_fed_shares_sent\",0],[\"files_sharing\",\"num_fed_shares_received\",0],[\"encryption\",\"enabled\",\"no\"],[\"encryption\",\"default_module\",\"yes\"]]}",
      "last_sent": "1598265722",
      "php": "yes",
      "server": "yes",
      "stats": "yes",
      "types": ""
    },
    "suspicious_login": {
      "enabled": "yes",
      "installed_version": "3.2.1",
      "types": "authentication"
    },
    "systemtags": {
      "enabled": "yes",
      "installed_version": "1.9.0",
      "types": "logging"
    },
    "tasks": {
      "enabled": "yes",
      "installed_version": "0.13.3",
      "types": ""
    },
    "text": {
      "enabled": "yes",
      "installed_version": "3.0.1",
      "types": "dav"
    },
    "theming": {
      "cachebuster": "26",
      "color": "#020442",
      "enabled": "yes",
      "installed_version": "1.10.0",
      "name": "TorbenArneCloud",
      "slogan": "***REMOVED SENSITIVE VALUE***",
      "types": "logging",
      "url": "***REMOVED SENSITIVE VALUE***"
    },
    "twofactor_backupcodes": {
      "enabled": "yes",
      "installed_version": "1.8.0",
      "types": ""
    },
    "updatenotification": {
      "calendar": "2.0.4",
      "contacts": "3.3.0",
      "core": "19.0.3.1",
      "documentserver_community": "0.1.7",
      "enabled": "yes",
      "files_accesscontrol": "1.9.1",
      "files_antivirus": "2.4.1",
      "files_markdown": "2.3.0",
      "files_mindmap": "0.0.22",
      "files_rightclick": "0.15.1",
      "flowupload": "0.1.8",
      "groupfolders": "6.0.7",
      "installed_version": "1.9.0",
      "mail": "1.4.1",
      "news": "14.1.11",
      "notes": "3.6.4",
      "passwords": "2020.8.0",
      "phonetrack": "0.6.4",
      "piwik": "0.6.0",
      "richdocuments": "3.7.4",
      "richdocumentscode": "4.2.800",
      "spreed": "8.0.10",
      "suspicious_login": "3.1.0",
      "tasks": "0.13.3",
      "types": "",
      "update_check_errors": "0",
      "user_usage_report": "1.2.3"
    },
    "uploaddetails": {
      "enabled": "no",
      "installed_version": "0.1.3",
      "types": ""
    },
    "user_ldap": {
      "background_sync_interval": "1800",
      "enabled": "yes",
      "installed_version": "1.9.0",
      "types": "authentication"
    },
    "user_usage_report": {
      "enabled": "yes",
      "installed_version": "1.3.3",
      "types": "filesystem"
    },
    "viewer": {
      "enabled": "yes",
      "installed_version": "1.3.0",
      "types": ""
    },
    "workflow_script": {
      "enabled": "yes",
      "installed_version": "1.4.0",
      "types": "filesystem"
    },
    "workflowengine": {
      "enabled": "yes",
      "installed_version": "2.1.0",
      "types": "filesystem"
    }
  }
}

uname -a
Linux home.torbenarne.de 5.8.0-1-amd64 #1 SMP Debian 5.8.7-1 (2020-09-05) x86_64 GNU/Linux
Apache or nginx version: 2.4.46
PHP version: 7.4 php-fpm over fcgi

The issue you are facing:
When I open the webdav in nautilus I get an timeout (EDIT: It says Gateways Timout on the android client) (after login)
Also, when I try to upload a file via any client it stops at 100% and says the expected bytelength was higher than it recieved (detailed errors below, it always recieved about 120kb)
Is this the first time you’ve seen this error? (Y/N): N

Steps to replicate it:

  1. Upload a file or open the webdav

The output of your Nextcloud log in Admin > Logging:

{"reqId":"X1vnlTkOo9AFBZC6YsaqrAAAAAc","level":4,"time":"2020-09-11T21:10:00+00:00","remoteAddr":"CENSORED","user":"Torben","app":"webdav","method":"PUT","url":"/remote.php/dav/uploads/Torben/95f3802862d80b7a52f7bfefd6cf44b8/0000000000000000-0000000005217695","message":{"Exception":"Sabre\\DAV\\Exception\\BadRequest","Message":"Expected filesize of 5217695 bytes but read (from Nextcloud client) and wrote (to Nextcloud storage) 114688(AUTHORS NOTE: There are several typical vaules here all around 100kb) bytes. Could either be a network problem on the sending side or a problem writing to the storage on the server side.","Code":0,"Trace":[{"file":"/var/www/cloud.torbenarne.de/apps/dav/lib/Connector/Sabre/Directory.php","line":154,"function":"put","class":"OCA\\DAV\\Connector\\Sabre\\File","type":"->"},{"file":"/var/www/cloud.torbenarne.de/apps/dav/lib/Upload/UploadFolder.php","line":46,"function":"createFile","class":"OCA\\DAV\\Connector\\Sabre\\Directory","type":"->"},{"file":"/var/www/cloud.torbenarne.de/3rdparty/sabre/dav/lib/DAV/Server.php","line":1104,"function":"createFile","class":"OCA\\DAV\\Upload\\UploadFolder","type":"->"},{"file":"/var/www/cloud.torbenarne.de/3rdparty/sabre/dav/lib/DAV/CorePlugin.php","line":527,"function":"createFile","class":"Sabre\\DAV\\Server","type":"->"},{"file":"/var/www/cloud.torbenarne.de/3rdparty/sabre/event/lib/WildcardEmitterTrait.php","line":89,"function":"httpPut","class":"Sabre\\DAV\\CorePlugin","type":"->"},{"file":"/var/www/cloud.torbenarne.de/3rdparty/sabre/dav/lib/DAV/Server.php","line":474,"function":"emit","class":"Sabre\\DAV\\Server","type":"->"},{"file":"/var/www/cloud.torbenarne.de/3rdparty/sabre/dav/lib/DAV/Server.php","line":251,"function":"invokeMethod","class":"Sabre\\DAV\\Server","type":"->"},{"file":"/var/www/cloud.torbenarne.de/3rdparty/sabre/dav/lib/DAV/Server.php","line":319,"function":"start","class":"Sabre\\DAV\\Server","type":"->"},{"file":"/var/www/cloud.torbenarne.de/apps/dav/lib/Server.php","line":320,"function":"exec","class":"Sabre\\DAV\\Server","type":"->"},{"file":"/var/www/cloud.torbenarne.de/apps/dav/appinfo/v2/remote.php","line":35,"function":"exec","class":"OCA\\DAV\\Server","type":"->"},{"file":"/var/www/cloud.torbenarne.de/remote.php","line":167,"args":["/var/www/cloud.torbenarne.de/apps/dav/appinfo/v2/remote.php"],"function":"require_once"}],"File":"/var/www/cloud.torbenarne.de/apps/dav/lib/Connector/Sabre/File.php","Line":238,"CustomMessage":"--"},"userAgent":"Mozilla/5.0 (Android) Nextcloud-android/3.13.0","version":"19.0.3.1","id":"5f5be7e7be27a"}

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

[Fri Sep 11 23:11:14.011013 2020] [proxy_fcgi:error] [pid 141175:tid 140122986845952] (70007)The timeout specified has expired: [client CENSORED] AH01075: Error dispatching request to : (polling)

The output of your Apache/nginx/system log in /var/log/____:
(Should be no problem as SELinux is currently only permissive/deactivated)

Sep 11 23:11:26 home kernel: [247223.959763] audit: type=1400 audit(1599858686.583:34524): avc:  denied  { read } for  pid=141175 comm="apache2" name=".htaccess" dev="sda1" ino=3697691 scontext=system_u:system_r:httpd_t:s0 tcontext=unconfined_u:object_r:unlabeled_t:s0 tclass=file permissive=1
Sep 11 23:11:26 home kernel: [247223.959777] audit: type=1400 audit(1599858686.583:34525): avc:  denied  { open } for  pid=141175 comm="apache2" path="/var/www/cloud.torbenarne.de/.htaccess" dev="sda1" ino=3697691 scontext=system_u:system_r:httpd_t:s0 tcontext=unconfined_u:object_r:unlabeled_t:s0 tclass=file permissive=1
Sep 11 23:11:26 home kernel: [247223.959787] audit: type=1400 audit(1599858686.583:34526): avc:  denied  { getattr } for  pid=141175 comm="apache2" path="/var/www/cloud.torbenarne.de/.htaccess" dev="sda1" ino=3697691 scontext=system_u:system_r:httpd_t:s0 tcontext=unconfined_u:object_r:unlabeled_t:s0 tclass=file permissive=1

EDIT:
I set the FcgiTimeout in apache to 3000000 and the script timeout so somewhat over a minute

EDIT 2: The nautilus timeout was caused on my side. I am able to view all files, but uploading results in the same error as on the android client.

any idea how I could catch the bug or narrow down the cause for this error?

anyone? should I ask the devs on githuub?

So, conitued testing and tried new things until I discovered that apache2 has 3 TIMEOUTS, so I modified following values:
/etc/apache2/apache2.conf:Timeout 600
/etc/apache2/apache2.conf:ProxyTimeout 600
/etc/apache2/mods-enabled/fcgid.conf:FcgidConnectTimeout 300000

After setting above values, the problem seems to be resolved. Anyone with Gateway timeouts with or without php-fpm should try setting those values higher