Been there / Done That with the OVP nut..
Don't forget to make sure you have your radio code before you disconnect bat. power .....

..also, while 90% of the time a bad Starter Lock-Out sw [ that's German for NSS] solves the problem, be aware that both a worn ignition switch and a bad starter holding coil [ solinoid] ] will display the same conditions..
so. we will follow this to the end, just in case ..