So,
yesterday there was another viewing. The thing with the basement, it is only one corner. That was the former coal cellar. According to the measuring device, the basement is slightly damp (rubble stones, it is the same at my parents-in-law’s).
The windows are from 1996, I specifically checked again.
Regarding the roof hatch, yes, it is an attic and therefore no hatch was installed because it is too small anyway.