Im back and it is solved ! It was no bug in MA3
First i checked this "When you ran dxdiag, did you also 'Test Direct3D'? - ie. The Display tab in dxdiag should state that 'Direct3D Acceleration is Enabled' This can be found in the 'DirectX Features' box. If so, try clicking on 'Test Direct3D' to ensure that the 3D acceleration is functioning properly." but everything was fine.
But i had the feeling that my computer was slow so i checked with malwarebytes
http://www.malwarebytes.org/
Malwarebytes found a trojan and removed it, afterwards MA3 runs like hell
Im always very carefull in what i download but yes i was infected
Very strange that malware could interfere with a screensaver?
Anyway thanks everyone for the help !