If you cannot remove the damaged vehicle from the tracks, are you required to alert the train driver about the potential danger?

Yes. Under Art. 28 para. 5 of the Road Traffic Act, if a vehicle becomes immobilised on a railway crossing, the driver must remove it from the tracks at once, and if that is not possible, take action to warn the train driver. You can do this by calling 112 or the emergency number on the plate at the crossing, which lets the train driver start braking in good time.