NextCloud 14.0.10+DSM Synology 6.1

Synology DSM 6.1.4-15217 Update 1
NextCloud 14.0.10
Apache 2.4
PHP 7.2

Good day, everyone. Sorry about my English.
I have such a problem - NextCloud overwrites the rights to the directory in which user folders are created when registering on NextCloud.
Describe process: - to Synology there are two options access: 1) External users who register on NextCloud and upload their files. 2) Superusers who go to Synology and using FileStation save these files to their computer.
The problem is that each SuperUser has access to certain users, for example:
Super1 has access to the directories user2, user3 and user5. And Super2 has access to the user1, user4 and user6 directories.
I configure the access I need through the Synology interface=>Control Panel=>share Folder=>Permissions. Everything works until some user comes to NextCloud. Then all rights are reset to the default (those that are registered for the user and group on which NextCloud is running).

Not familiar with Synology, but it is right. As soon as NC user comes in he will create files that will belongs to the Synology system user that running nextcloud application on Server.
Running nextcloud process as e.g. www-data user then all files from all nextcloud users will belongs to www-data user.
So you have your user management twice:

  1. On Synology server you will give access to Application Nextcloud.
  2. On Nextcloud you will create users and give them access. From the Synology point of view they will be all one user that you configured in point 1. Except if you bind your Nextcloud to Synology IAM via e.g. LDAP or other mechanisms.