Can someone still developing tell me what I should use for the backend today?

I recommend checking out Python (Django) and Ruby (Ruby on Rails) if you want nice and easy modern Web frameworks that also aren't that weird if you have PHP experience.

Also I can never understand GIT as a single developer. The fuck is that? I've tried everything to understand.

Versioning your code with Git makes it much easier to experiment with new ideas. Cocked up a file? Pull it from the previous version. Create new branches for experiments, merge them in if they work, toss them if they don't, or keep them around just in case, without them ever getting in your way in the "real" version.

And if you keep the code in a server (GitHub etc), that gives you a backup location and makes it easier to work on code on multiple systems.