I pressed Connect in the software before I switched on the machine. Nothing happened, as supposed.
After switching the machine on and pressing connect again all axis startet to move at fastest speed , crashing very hard before I could press the estop, damaging the nozzles, part of the feeders.
I guess I need a whole new calibration now if the motors are still intact, we'll see.

So take care not to do that on your machine, there is not safety to prevent wrong startups.