I want to build a website where users can upload screenshots from movies. Does anybody knows if this is (il)legal? I'm living in europe/germany.
It depends on a few things - are you charging people to see the content on your website? Do you have the copyright info for the movie (e.g. ©2009 Universal Studios) shown under the image? And what size image are you showing?
I'm certain that if you charge people to see a 1080p-resolution image capture from a movie, you'll be running into some issues.
However, if your site is more of a simple movie review site or service, and you are displaying a small image capture of a scene from a movie, that would probably be considered fair-use.
If you're running a pretty large site, though, I'd ask a lawyer.