Yesterday I got an alarm of the Battery/Generator. In the instructions it is said to stop the car immediately.
What could be the cause?
I've installed a brand new battery recently. I don't understand what might be the problem.

 

I don't think anybody else will without looking at the car in more detail, either.

After checking the battery, connections, etc., if the alarm persists I would get it to a dealer or a good Porsche service technician. Could be any manner of electrical problems and they tend to get serious, quickly, if not attended to.