thanks for the feedback!
I am right now at my girlfriends place. So I can´t have a look into the MacBook Pro.
I hope that it is only a cable ..:-(
@lemerise: I have connected the MBP to an external monitor and there are no purple lines.
@lemerise: I mean preasure on the MBP case. Sometimes the lines disapear also when i move the display up and down....Its very strange.
@markus: Do u know where this plugs , that can get a little lose, are? Where can i find them on the board? thanks M.