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:

I have already tried the following:
and unfortunately didn’t know what to do from here on

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?