Sale of my used / problems

Hello forum, I’m thinking about a short question: I sold my used car 4 days ago. (about 10 years old) The buyer has tried driving, looked at the car and made a purchase contract with me. All details have been held, handed over the papers etc… Now the buyer calls me and says that the clutch is no longer the best and that the car allegedly had an accident damage. I bought the car “accident-free” used, documents exist, would In my time, no accident happens either. Accordingly, the car is accident-free from my point of view. The buyer now threatens with a lawyer because of these points. What is ahead of me? What can happen to me, what do you think? Thank you for your help and quick answers.