Is the garage holding up for fuss?

Hi, a friend of mine had to be towed in June of this year. At that time the WaPu disassembled it because it missed the interval for the timing belt change relatively long. A workshop then made everything new. Since then it has driven a few thousand kilometers. I do not know the exact running performance (at that time and today). Last week it remained lying down again. Towed to another workshop, which probably said that the timing belt wrongly mon I can’t judge if that’s true – I haven’t seen the car/engine itself yet yet. Does the workshop have to be responsible for this, which has pulled the crap out of it? If so, on what legal basis? Is one in the obligation to prove that nobody else has done anything about the engine in the meantime? Thank you very much! Sven PS: If the topic is wrong here, please move it to the correct forum.