UPDATE!!
Finally we call the help of an external mobile service. They charged the V12 battery and we could charge the car again. But there were still errors re the v12 battery.
We made an appointment at Tesla service. They checked and replaced the battery under warranty. Great job at the end. I already forgot about the Tesla service manager who did not wanted to send a mobile support to fix it by Tesla from the start. Could have saved me a lot of frustration. Because the Car is excellent!