Sold car with false engine number not as natis report

Bought car on auction with derka reporting engine oil leak before I collect got a call from sales rep that car now got engine nkock and later car at my mechanics we discovered that engine is not same as what is natis or vehicle disc now no help from we buy cars though reported two weeks before I took my car out and answer from complaint department (wellem) that cars are sold as is on auction so derka is overridden and false engine number is legalized so now I don't nkow what to do either to go to police or to media or to lawyers