Car purchase/(fraud)?

Hello together, the following happened to me,I bought a car privately Bezw. a Smart..;-) Number of previous owners 1,check booklet maintained, everything sounded good,the seat heating is a fault with the passenger but should be quickly fixed by a fuse,it happened recently, later it turned out that the heating already with the previous owner defect, Yes.. there it goes, at the registration office I have on the new vehicle letter(the old one was invalid) that I am now the 4 owner.. The complete checkbook which he sent to me later with the post was not complete at all, instead up to 98,000 only up to 35,000. I tried to contact the seller but in vain, suddenly left for 6 weeks to Pakistan. After 2000 km the smart went out on the highway, towed to the workshop and then the great horror,total damage..Car bought for 3000, repair costs 3700,- Euro.. The seller refuses to pay a cent as I today from the arbitration office. I don’t know what to do, the lawyer would also cost me money, how are my chances? I have 2 witnesses who can confirm his statements,1 hand and checkheft complete..nothing was right about it..is dealing with an ADAC adjournment (blue) for car sales.I hope you can help me, am in despair… Greeting Timi2