VW POLO sold, defect buyer wants money back

Hello, before the Christmas days I sold my VW Polo 6n with approx. 160tkm. During the visit I indicated all the defects known to me and also noted in the purchase contract, the contract was an ADAC form which excludes the liability for defects in material defects. In addition, I registered for defects ‘age and mileage caused defects’ as well as under special agreements ‘All damages from delivery at the expense of the buyer’. At the inspection the buyer fell on which the engine runs restlessly, Si e probably had the same engine in a gulf. But since I am an absolute layman, I didn’t notice that, it didn’t think it was very unusual, because I didn’t notice it when driving. In idle, there were minimal speed fluctuations, which I also said during the inspection. However, I didn’t notice this restless run in the contract, because I didn’t think it was unusual. Today came the call, there was a coming engine damage, she would have hereits invested money for new candles and ignition cables and had the engine pressure (??) measured, whereby it was noticed that the third cylinder has only 6 instead of 10 bar pressure. However, since I am not aware of any fault, I told her that accordingly, she wants to become a lawyer now.. Should I be worried? LG