Construction costs for a single-family house built in 1895?

Dear members,

we are planning to buy and renovate a single-family house from the year 1895. The living area is 96 sqm and is heated with a gas heating system from 2012. Electrical installation, windows, and pipes were also renovated in 2012. All rooms (bathroom, kitchen, bedroom) were modernized in 2012 as well. We would like to convert the attic into a gallery, as we currently lack a bedroom. The roof would need to be renovated.
We also want to build an extension (wood cladding on the outside) to have additional space for a dining room (conservatory). We also plan to bring the house up to the latest energy standards (heat pump; solar system) with underfloor heating.
What would such a conversion cost?
- gallery conversion with stairs
- new roof
- conversion from gas heating to heat pump (solar system)
- underfloor heating
- extension max. 15 sqm

Best regards

You should still have 180k +/- 50k. But for financing, you need reliable offers. A forum is not sufficient for that.

What would such a renovation cost?

That can only be answered in general terms with "from... to" or "42". You would have to show the house much more precisely (photos, drawings from the building file). The year of construction 1895 suggests that the foundation was already made quite differently than is usual today. You should inspect the house with professional guidance. How far is it from Bad Münstereifel (ZIP code 539)?