Well first of all i have to say what exactly my problem was: The screen was a bit loose in the right bottom corner so that you could press it down. But there was no loud clicking noise, only a very silent one, not a so big problem, i mean there was no noise that would have been a problem. The screen isnt glued.
Yesterday i had my appointment at the genius bar, i showed my phone one of the employee, he immediately recognized my problem and checked if the frame was warped or if its a "problem of the screen". He said that the frame is okay and that he will simply unscrew the display and will screw it again on the frame. He did that in the workshop. When he was done he showed me the phone and the loose screen was gone...till today the screen is absolutly fixed, no loose screen. Great!
He said if the screen gets losse again ill get a new scree, and if the problem would even appear with the new replacement screen i'll get a new phone.
But till now the screen is abolutly fixed!
He said that it looks like that the screen does not lock in all areas so that the screen hast to be unscrewed and screwed on again so that the screen locks in all areas of the phone. Looks like exactly this was my problem.
I also checked all the phones in the apple store, none of the phones had a loose screen in one of the edges! Simply no one! I couldnt believe this because a lot people here wrote that all of the iPhones have that "loose screen problem"...doesnt look so...
Now i hope that the screen keeps fixed and doesnt get loose again. I'll let you know if the screen gets loose again.