Finally, a coach is willing to check my form...
 

Not that I tried this seriously the last years, but now I found indeed an old and quite successful weightlifting club in my area (~70km from me) and one of the coaches, a competitive weightlifter for the last thirty years (PRs snatch: ~92.5kg C&J: 112.5kg @ 69kg) is willing to look over my shitty technique. I would consider my selftaught 'technique' hopeless but I will try if that is indeed the case.

Good. Do what he says.