Thank you for the answers. We will definitely carry out an inspection with a building expert. According to my layman’s understanding and the impression on site, I found the roof (concrete tiles) to be okay. The electrical system is of course already three-core with an RCD, but original. The bathrooms were renovated 12 years ago, and in that context probably also parts of the wiring. Overall, the wiring is original aside from that. The heating system is also 12 years old. Certainly, a replacement investment will be due in the next 8-10 years. I am currently planning what the absolute must-do measures are and what can presumably stay as is for now. I come to the conclusion that external wall insulation including plastering and the replacement of the old windows are very sensible and necessary measures. I am of course always grateful for suggestions on what (somewhat affordable) measures others consider sensible for similarly old properties (as well as for the really very pleasant exchange here in the forum). Best regards