Engine damage on the transfer after 90km

Hello together, I have a big problem: I bought a Saab 900 2,3SE convertible from Privat, BJ 1995, 197,500km with brand new TÜV and AU. The car should be completely OK. In the preliminary interview and the display was given: “Cylinder head seal is made”. There was a first meeting with a short test drive. Here it turned out that the roof did not work perfectly. There was also a somewhat strange, turbine-like noise at the cold start, which after The seller said that he had the car for 4 years and that this sound was normal. He also referred to the fresh TÜV acceptance and some minor repairs in a workshop – everything from the day before. “Cleaning, driving, having fun, there is technically everything in order” was the announcement. We agreed that the seller should repair the roof and we then meet again. After two days I got the message that the roof is now better than the roof. I live about 120 km away and the seller in a very rural area. We arranged that he would pick me up at a train station about 50 km away from him, which he did. He came up with the Saab and I was surprised that the car seemed somehow nailed – I have been driving only diesel for 30 years and found the sound too familiar to get a deep shock immediately, but would have the sound of a 2.3 liter Be The seller, who came with his neighbour and was quite sympathetic to me, said that he did not hear anything unusual, the engine was fine, he had now also driven the whole track without any problems. We drove to him home – first through the city, then highway. 20km before the finish I took over the steering wheel. The car pulled reasonably well, braked well and was surprisingly quiet in the interior. I brought again m a perception of nailing into the game and seller and his neighbor referred to the steering chain, which after almost 200,000 km could not work completely noise-free. I thought: The car was just in the workshop, has been examined and is over 20 years old… I am paranoid and small-carried… And bought and made me on the way home with the thing. After about 1 hour and 95 km drive at 120km/h through night and rain suddenly rapid power loss and While I was still guessing what might be going on, sudden massive noise of the very unhealthy kind from the engine compartment. I was just at the height of a motorway descent and could still take it. In the descent all the lamps were already on, the engine was off. The friendly ADAC man meant only: bearing damage. Shit. Contract was standard form with exclusion of warranty except with gross negligence and intent. How do you estimate this?