Docker Container, redirect?



I’m new to Yunohost. It is a great peace of software.
I have installed it on a VPS and everything works proberly.

My Problem: I need a few more Applications. Which are not available as app,
for example groupoffice. I’m not able to make a app package.
For testing I installed Portainer as Container with port 9000. Serverip:9000 works great.

And now I need to make a sub.domain and forward it intern to the docker Container.
I try it with the redirect app. I have a dashboard icon. And that redirect to the portainer
Login Page. But I can’t login. The same with Ajenti I installed (no docker) when I log in
the Site freezes.
Is this a buck in the redirect app?
What are right settings in the redirect app? (I use proxy invisible)
Is there a better way to make Container available as sub Domain and in the portal?
What is the right way to get a certificate for the docker applications?
(SSO is not so important)

Thanks for your help!