Thank you for your opinions!
Yes, the social environment, I would say, is also an important point for me. Around the old building, there seem to be "tolerant" people living nearby, but in that part of the district definitely many "older generations." In the new development area, around 60 residential units will be created, half of which were directly allocated by the city but with Criterion 1: toddler or child already on the way. So we had no chance there because the first child is planned but so far neither here nor on the way. The other half went to 4 developers and 1 building community. One can assume that the majority here are families about our age with and without or not yet with children. Nearby, a new kindergarten and a school will be built next year.
Barrier-free. That is also important for us because my mother will move in. In the old building, there are half-spiral staircases and at the entrance there are also 4 steps, and at the terrace again 2 (without railing). In the new building, the ground floor would initially be level, to the upper floor there would be a straight I-shaped staircase, and if necessary, later on the ground floor the living/cooking/dining room can be reduced by inserting a wall behind the carport and thus create a room on the ground floor. Although the bathroom is also upstairs, with this staircase a lift would not be a problem in x years.
After I spoke with an ex-colleague who lives almost opposite the old building, we abandoned the idea of having an expert and are now concentrating only on the chance of the new building. She has an almost equally old house and was able to tell us about the previous owners, etc. The costs for renovation and refurbishment have no precise upper limit here, which would be too risky a game for us, among other things.
The building community from the new building has to choose us as "neighbour next door" or reject us by early September... I am nervous.