Motorbike against turning car: who pays?

Hello, imagine the following accident: a motorcycle comes from a driveway, flashes and drives to the driveway. From the next driveway behind comes a car and drives to the road. The driver of the motorcycle can no longer brake and shoot into the side. The driver who has taken the driveway from the motorcyclist will claim to the police afterwards he would have thought because of the turn signal the motorcyclist wants to turn next to in again and not straight white The motorcyclist still had about 3-4 s on the main road before he turned it off (logically, you always make it after turning it off). The consequences of the accident were very serious injuries to the motorcyclist (speed far below the permitted HG), minor damage to the motorcycle and the car. What do you think would come out of such a case of guilt distribution? What should the injured person or his family do about possible As a result of the hospital stay the biker has to fail several duties. I would be happy if you could give me a rough orientation. I am not involved in the accident but only friends with the motorcyclist. Greetings, winter