Derka from we buy cars are **** and poor service

Bought bmw 2010 325i e90 on auction with derka report stating that car has oil leak issue, so I bought and paid then about to go pick up received a call from them that the car has engine noise then I longed complain then Willem took my case and told me that auction principle nothing they can do, then I went collect the car and noisy was much then got stuck out of their gates then took with breakdown everytime I call wellem he say is working on it and then he said claim were rejected then I asked him to answer by email but no . Now car is at machenical and Engine number is not what is on disc and engine looks very old than the car I need them to take full responsibility and not selling us cars with different engines