My problem is, that the camera of the player doesn’t follow the rotation of the vehicle. Location works fine.
You must understand how confusing all this is. This sentence alone opens an entire new can of worms. How are you checking the rotations: through the camera, numerically or visually (eject and visually check its orientation)?
Is your camera attached to a springarm? Does the spring arm (if any) have “Inherit Yaw” checked?