Wordpress read-only local volumes (NAS)


Have a Docker yml-file for setting up a Wordpress environment and mounting to a map on my Qnap NAS Container Station. (https://www.qnap.com/en-uk/how-to/tutorial/article/how-to-use-container-station/)

After building the WP container all my files are added to the map. So far so good!

But the map in the NAS after mounting the container is read-only. Trying ‘fix’ the permissions (Control Panel -> Shared Folders), but after restart the container; the container doens’t use it anymore.

This is my yml-file i used:

Is there a solution set the permissions in the yml-file?
After searching and trying several solutions, thinking it is not only WP specific, but the dir /var/www/html has not the right permissions??

I read a lot about this problem, but the most things i found is used by the command-line.
I hope there is a ‘simple’ solution for this and someone has experience with Docker on (Qnap) NAS?