Complex sentence: The incident worsened when they had supposedly went by car, where Stan had started to beat him with her legs, to which Prodan had acted in self-defense, and ultimately had slapped her after she had pulled the wheel to the right.
Split into simpler sentences: The incident worsened when they had supposedly went by car, where Stan had started to beat him with her legs, to which Prodan had acted in self-defense. He ultimately had slapped her after she had pulled the wheel to the right.