Great, th'as up and running, now The certificate is valid and my browers and other apps are happy!
Thank you again for the help and the great job with all those docker add-ons! Sorry if I missed some information in the docs sometimes, but one can admit that there are a lot of sources of information: your website, readme files, multiple forum posts here... And some of them are outdated, so it is quite hard for a beginner to find the right information.