Hey everyone,
but I was not able to turn them off (I have tried all the combinations, what can close the computer game on PC)
The key combination you are looking for is CTRL-AMIGA-AMIGA, which resets any Amiga and is comparable to CTRL-ALT-DEL on a Windows pc.
The 'Amiga'-keys are next to the spacebar (left & right) and are marked with an 'A'. Quite often, the left Amiga key is marked with the Commodore logo instead of the Amiga logo .