Nextcloud nginx adfs

i am new the forum. So thanks in advanced for your help!
I have successfully build an nextcloud instance on an ubuntu 20 server with ssl enabled and ADFS authentication working.
But i have to get the ADFS SAML authentication think workting on a Nextcloud Docker instance that is running behind an nxing reverse proxy.

The nextcloud is working. That is not the issue. I am able to open the website with my company ssl certificate that was created for the nginx server. But the SAML configuration is not working. I have no idea how to fix that.
I think the issue is, that the container inside is not using https. In the logfile of my adfs server i see that the website that is returning the error begins with http.

I had the same issue on my ubuntu box. But after changing the default redirection for the apache to https, adfs was working. I was able to download the xml file with the correct settings.
I am working on this for days now without any result. So i was hoping to get some sort of ideas from the forum.

Thanks for any hints on this.