Thank you. I watched the video, which is very helpfull. But I had configured everything the way it should be.
For the Matrix cliet I use nheko. I could register with nheko and log into my account.
I could make a new room and see the user i registered.
I tried to log in from another laptop in and outside from my home network. Unfortunately the homeserver was not found. Can the reason be, that I did not succeed in obtaining a certificate for matrix
In the topic " Let’s Encrypt “Failed to obtain certificate …”" is the descripton of what happened to me.