Exception Sabre Forbidden No read permissions

Hello, folks,
for some time now, when I open a folder in the Nextcloud IOS app in my mobile phone, I get the error message
RequestFailed: forbidden (403).
Here the decodede error message from the Nextcloud Log:
https://pastebin.com/kgZHgypM

I have already tried the following:
https://cweiske.de/tagebuch/debug-nextcloud-error.htm
and unfortunately didn’t know what to do from here on
https://cweiske.de/tagebuch/debug-nextcloud-error.htm#source-p9!

I also tried modyfing nextcloud-db with phpmyadmin and changed all permissions.
But i think they werent saved cuz I am using docker!

Rescanning the FileSystem didnt help either…

Do you guys have an idea?

Felix