Nextcloud - Proxy / need help - [SOLVED]

Hallo everybody please I need help on following probelme:

I have a revers proxy server (apache2)
and a virtual machine running Nextcloud on a server in the same network as the proxy.

Everything is working as it should be except for one thing:
When trying to reache https://mydomain.com/cloud it overwrites the URL to https://mydomain.com/index.php - no site was loaded, but when entering https://mydomain.com/cloud/ - everything works fine (okay the login is a bit wonky but I expect that is related to the problem)

Needt help plz!!!

here is my revers proxy site (redacted):

<IfModule mod_ssl.c>
 <VirtualHost *:443>
        ServerName mydomain.com
        ServerAdmin office@mydomain.com

   <IfModule mod_headers.c>
        Header always set Strict-Transport-Security "max-age=15552010; includeSubDomains"
   </IfModule>

        ProxyPreserveHost On
        RewriteEngine On
                RewriteRule ^/\.well-known/carddav https://%{SERVER_NAME}/cloud/remote.php/dav/ [R=301,L]
        RewriteRule ^/\.well-known/caldav https://%{SERVER_NAME}/cloud/remote.php/dav/ [R=301,L]

        ProxyPass /cloud  "http://xxx.xxx.xxx.xxx"
        ProxyPassReverse /cloud  "http://xxx.xxx.xxx.xxx"
        ProxyPassReverseCookiePath /cloud /cloud

        ErrorLog ${APACHE_LOG_DIR}/proxy.log
        CustomLog ${APACHE_LOG_DIR}/proxy.log combined

        SSLCertificateFile /etc/letsencrypt/live/mydomain.com/fullchain.pem
        SSLCertificateKeyFile /etc/letsencrypt/live/mydomain.com/privkey.pem
        Include /etc/letsencrypt/options-ssl-apache.conf
</VirtualHost>

NC apache2 site:

ServerName mydomain/cloud
ServerAdmin office@mydomain.com
DocumentRoot /var/www/html/nextcloud

here NC config.php (redacted):

<?php
$CONFIG = array (
  'instanceid' => 'xxxxxxxxxxxxxxxxxxxxx',
  'passwordsalt' => 'xxxxxxxxxxxxxxxxxxxxxxxx',
  'secret' => 'xxxxxxxxxxxxxxxxxxxxx',
  'trusted_proxies' =>
  array (
    0 => 'xxx.xxx.xxx.xxx',
  ),
  'overwritehost' => 'mydomain.com',
  'overwriteprotocol' => 'https',
  'overwritecondaddr' => '^xxx\\.xxx\\.xxx\\.xxx$',
  'overwritewebroot' => '/cloud',
  'trusted_domains' =>
  array (
    0 => 'mydomain.com',
    1 => 'xxx.xxx.xxx.xxx',
    2 => 'xxx.xxx.xxx.xxx',
    3 => 'xxx.xxx.xxx.xxx',
 'datadirectory' => '/var/www/html/nextcloud',
  'dbtype' => 'mysql',
  'version' => '18.0.0.10',
  'overwrite.cli.url' => 'mydomain.com/cloud',
  'dbname' => 'mydbnc',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => 'myuser',
  'dbpassword' => 'mypaswd',
  'activity_expire_days' => 14,
  'auth.bruteforce.protection.enabled' => true,
  'blacklisted_files' =>
  array (
    0 => '.htaccess',
    1 => 'Thumbs.db',
    2 => 'thumbs.db',
  ),
  'cron_log' => true,
  'enable_previews' => true,
  'enabledPreviewProviders' =>
  array (
    0 => 'OC\\Preview\\PNG',
    1 => 'OC\\Preview\\JPEG',
    2 => 'OC\\Preview\\GIF',
    3 => 'OC\\Preview\\BMP',
    4 => 'OC\\Preview\\XBitmap',
    5 => 'OC\\Preview\\Movie',
    6 => 'OC\\Preview\\PDF',
    7 => 'OC\\Preview\\MP3',
    8 => 'OC\\Preview\\TXT',
    9 => 'OC\\Preview\\MarkDown',
  ),
  'filesystem_check_changes' => 0,
  'filelocking.enabled' => 'true',
  'htaccess.RewriteBase' => '/',
  'integrity.check.disabled' => false,
  'knowledgebaseenabled' => false,
 'logfile' => '/var/log/nextcloud.log',
  'loglevel' => 0,
  'logtimezone' => 'XXXXXXXXXXX',
  'log_rotate_size' => 104857600,
  'maintenance' => false,
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'memcache.locking' => '\\OC\\Memcache\\Redis',
  'preview_max_x' => 1024,
  'preview_max_y' => 768,
  'preview_max_scale_factor' => 1,
 'redis' =>
  array (
    'host' => '/var/run/redis/redis-server.sock',
    'port' => 0,
    'timeout' => 0.0,
  ),
  'quota_include_external_storage' => false,
  'share_folder' => '/Shares',
  'skeletondirectory' => '',
  'theme' => '',
 'trashbin_retention_obligation' => 'auto, 7',
  'updater.release.channel' => 'stable',
  'installed' => true,
  'data-fingerprint' => 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx',
'onlyoffice' =>
   array (
      'verify_peer_off' => TRUE,
    ),
);

and nextcloud .htacces (only what I added):

<IfModule mod_rewrite.c>
Options -MultiViews
RewriteRule ^core/js/oc.js$ index.php [PT,E=PATH_INFO:$1]
RewriteRule ^core/preview.png$ index.php [PT,E=PATH_INFO:$1]
RewriteCond %{REQUEST_FILENAME} !\.(css|js|svg|gif|png|html|ttf|woff2?|ico|jpg|jpeg)$
RewriteCond %{REQUEST_FILENAME} !core/img/favicon.ico$
RewriteCond %{REQUEST_FILENAME} !core/img/manifest.json$
RewriteCond %{REQUEST_FILENAME} !/remote.php
RewriteCond %{REQUEST_FILENAME} !/public.php
RewriteCond %{REQUEST_FILENAME} !/cron.php
RewriteCond %{REQUEST_FILENAME} !/core/ajax/update.php
RewriteCond %{REQUEST_FILENAME} !/status.php
RewriteCond %{REQUEST_FILENAME} !/ocs/v1.php
RewriteCond %{REQUEST_FILENAME} !/ocs/v2.php
RewriteCond %{REQUEST_FILENAME} !/robots.txt
RewriteCond %{REQUEST_FILENAME} !/updater/
RewriteCond %{REQUEST_FILENAME} !/ocs-provider/
RewriteCond %{REQUEST_URI} !^/\.well-known/(acme-challenge|pki-validation)/.*
RewriteRule . index.php [PT,E=PATH_INFO:$1]
RewriteBase /
<IfModule mod_env.c>
SetEnv front_controller_active true
<IfModule mod_dir.c>
DirectorySlash off
</IfModule>
</IfModule>
</IfModule>

Nextcloud version: 18.0.0.10_
Operating system and version: Ubuntu 18.04
Apache or nginx version: Apache 2.4.25
PHP version: 7.3-fpm

okay the problem is solved!

A simple rewrite-rule did the job!
If someone have the same problem in the apache2 site (on the Reversproxy) add:

RewriteRule /cloud$ https://%{SERVER_NAME}/cloud/ [P]