First of all, welcome!
You could take a look at the different demo layouts to understand the simple and complex mechanisms needed to make things work. Looking at a teamwork/wandernetz might also help. If you want to start building with other people, better learn German

There hasn't been any development on this project for 1½ years, although if more people want I'm sure it can be revived.
Seeing as BAHN is a German program, most of the documentation is in German. Google translate can help, but sometimes it's just trial and error. I might be able to help you, but compared to others, my knowledge doesn't cover everything.