Hey, thanks for your answer
i followed the steps [1] and [2] did not work, although when i pressed CRTL+ALT+'+' the InputNotSupported went away and i saw some colorful weird lines.
so i booted in "text" mode, hit tazx pressed "install ati driver" a minute later i was back in the commandline
so i typed "X" to start the Xserver i guess, it started and the screen was just Black. There was no "InputNotSupported" just black.
so i hit CTRL+ALT+F1 to get back to command line
there was some error regarding my mircrosoft wireless keybord, and a warning regarding some KEYBOARD stuff, but nothing else.
i also looked at the xorgconfig files
the ones under /xorg.conf.d
for example 50-Monitor.conf recognized my monitor correctly
under 70-Screen.conf there where different Depths but no "Modes", so i added some to the SubSection which had "Depth" 24.
i also looked at the log file, but i didnt see obvious errors marked with (EE)
so im pretty clueless what to do next