Question about the behavior of the seller

Hello together, I looked at an Audi A4 year 2001. The car is sold by the owner’s son, since the owner died. I checked everything and names etc. are identical of both persons, so it is not a supposed dealer. Kilomerstand could also be traced to the Tüv reports etc. and the car is also really good there. The car has only until March 2018 Tüv and I asked the seller if he is ready with me to the Tüv and to renew it again. He explained himself ready and assured me that the reperatures which would still occur would go down from the price. The 30.10. was agreed because he himself is away a week. Now he then called me afterwards and asked if it would be right tomorrow, his brother would then come with us to the Tüv, as otherwise this would take him too long. Then somehow the alarm bells went on with me, because ic h can’t quite understand why you can’t wait a week. Well, I’m always very suspicious in general, I mean after all, the car is checked by the Tüv yes and if what’s on it is not reduced then I can refuse. What do you think? Is the behavior of the seller funny or am I too suspicious? Thank you in advance.