Finally, I'm able to play the game!
Wether the latest patch, a recent windows update or me disconnecting my oculus rift was the reason, I can not say, since all of this happened just before my first successfull login.
I just wanted to try it without the rift, but when I restarted my PC, windows installed an update and when I started the game, it downloaded a new patch.
Now I can start the game and when it works, it's absolutely stable, played 4h and no problem at all.
Sometimes it still crashes after loading, but until now I just tried it again and it worked.
I still play with the absolute minimum graphics settings, when I tried to activate shadows on low, it again kept crashing after loading.
It seems like anything above just calculating simple voxels/elements is too much at the moment. I hope in the future I will be able to enjoy better graphics, but for now I'm happy that I can play the game.