It's a bug in the game, try clicking the mousebuttons a few times, it should go away.

Thanks,
for the tipp, sadly I didnt have any mouse activated. I play on a notebook and use USB-Keyboard, External drive and a Thrustmaster. So no more room for a mouse.

But it should have something to do with the mouse, when I tried today again, it somehow worked. This time I disconected the mouse and startet with the touchpad on the notebook, and "tada" no problem at all. Before I started with mouse and changed than to Joystick, maybe that throw it off.