Wow! Nobody else has mentioned anything like this!
Seriously - if you'd looked before going into full-on rant mode, you'd have seen umpteen posts about Lr's current performance issues.
Many of those posters even have provided some useful information about their operating systems and the like - you know, stuff that matters for troubleshooting - rather than just indulging themselves in a pointless tantrum.
So search the site, or at least have the courtesy to provide some intormation about your kit - especially the OS - because posts like yours don't fly here.
you are right. I was under pressure and lightroom had this bad performance. After posting I found the answer in another post, unchecked the Graphic card and the photo screen and now it works nearly perfect. I still got a little problem with uploading photos on my host from the web-module. Lightroom doesn't get access on every pic. But I first have to check other data.
Sorry for my full-on rant mode