Nextcloud Apache2 Reverse Proxy problem

I have a problem with a reverse proxy configuration ,witch I can’t find a solution for it. My nextcloud configuration is working fine with DynDNS over the internet ,everything is green at the Security & setup warnings. When i connect locally over Http is also fine. But after my reverseproxy setup im getting this famous warning.

The reverse proxy is in a separate container on Ubuntu 18.04. there is my config: Screenshot from 2020-05-03 20-10-13

Again I’m just started to learn this stuff ,and I really want to know whats the problem is? Can maybe put some more light on this issue?

also here is the conf file from the apache where nextcloud is running.

Anybody ?? any idea?

If you click on the link in the warning, it tells you how to fix it.

I have done this, no solution there to this problem