I want to make a copy of a movie, with menus and everything extra, but I want to remove the subtitles I never use and the Audio-channels I never use. What is the easiest way?

Ii it to use DVD Decrypter and then burn everything with Nero or something?

what you need to find is a proper tutorial m8, try over at doom9 or look at rishardc's Newbie DVD to DVD-r Guide at the beginning of this forum. Its not just a case of removing what you dont want then burn it has to be re-auth'ed as well.