Logic Question Related to SSL

Hi, I am doing fresh install and I would like to ask for just a logic question related to SSL.Now I can’t login to localhost but before configuring postfix-fetchmail-dovecot I was able to login to RT from localhost:80. Therefore I began to search for what I did wrong back in the history, and I realised that I was lack of server certification.
So I kept up searching on it to make my own, that didn’t work. Then I tried by Certbot, but that didn’t work neither, but also gave me such an error which says that my server is not .TLD and as I see without .TLD server its not even possible to make a SSL Key.

My question is, how can I manipulate the Apache such a way, that it will think that my localhost ends with .TLD and somehow it will keep up working with RT.

Or the easiest way to ask, how can I make this authentication in localhost for RT, well as I wrote I tried everything on websites that’s why I am writing here as last hope.

Or as suggestion should I just format the computer and restart, because while I was playing over with configs, maybe I edited sth wrong there.

Best Regards