Effectiveness of inspection and exhaust testing

Hi, I have a big problem, but I bought an A4 TDI 1.9 b5 Bj99 a year ago. Before the purchase, the car was in the inspection and passed an exhaust gas test successfully, but broke three days later. Result of total engine damage. Now a procedure is running against the dealer, the problem is he relies on the inspection and the exhaust gas test. This seems to me to be impossible to prove the opposite. I have very big financial problems we The car cost 1000€ at that time. I have inverted so much money into the car, you can expect to drive at least 1 year without any problems. My question now to you is: How meaningful are such inspections in the Audi contract workshop or exhaust gas tests. Both were successfully passed, but after approx. 1000km the car had engine total damage!!! How can s The court is now against us on the basis of these facts. He asserts that the damage AFTER the purchase, i.e. 3 days after receipt of the car, should have occurred. 1.Theory: Turbocharger defective dadruch was drawn oil in the diesel combustion room and the engine damage occurred.(Unfortunately, the case is excluded by the exhaust gas examination, which he had previously unmasked the defects:-( ) 2.Theory: Valve torn in the engine room and thus the engine damage should have occurred. D a this damage can occur at any time, so I stay at my expense. But I can’t believe that something like this can happen after 3 days. Can you do something about it? Are such inspections and exhaust gas tests really so meaningful? I really hope you can help me further I would be very grateful. Thank you With kind regards Lankan