Single-family house from 1950 with backlog of renovations "Charm of the 50s" - renovation costs

The floorboards will be normal spruce.
You cannot install triple glazing in 70-year-old spruce windows.

All the windows are made of plastic. Honestly, I don't know about the floorboards – so spruce floorboards cannot be refinished?

you cannot install triple glazing in 70-year-old spruce windows.

When I enter house 50s materials or similar on Google, various sites show me what the installed material was like back then and what renovations you need to plan for. For example, the quite thin walls and the low-quality wood with a narrow cross-section …

All windows are made of plastic.

That overlaps with my statement. If plastic is installed there, a modernization has already taken place.

Our subjective impression. For a house that is 80 years old and has never been renovated/modernized, we found it positive.

To be honest, I value this statement very little: you are laypersons. Even regarding an existing modernization (where, as is well known, many mistakes can be made), I would not buy anything without an expert. And they will tell you what _must_ be done and what _can_ be done.

I'm just brainstorming briefly, could this roughly make sense?
Property - 550TE
Additional purchase costs - 50TE
Renovation - 250TE ---> does it always make sense to finance this through KFW / Bafa and finance it separately? Keyword funding etc.
Equity - 150TE (plus buffer)
(there is also a home savings contract: 100TE filled to 30%, with about 2.5% loan interest rate (we secured this years ago), no idea how to best incorporate something like this

monthly rate around 2500 euros plus (house reserve, insurance and ancillary costs) 800 euros = 3300 euros

Before I go to the advisor, I wanted to ask around here... ;)

That overlapped with mine. If plastic is installed there, a modernization has already taken place. To be honest, I think very little of this statement: you are laypersons. Also regarding an existing modernization (where, as is well known, many things can be done wrong), I would not buy anything without an expert. And they will then tell you what _must_ be done and what _can_ be done.

Sorry, so the windows were replaced in the 1980s (whether that makes it better ...)

Let's put it this way: if the house itself is appealing, then with some renovation effort you can turn it into something worth the cost and work. With own labor and/or lots of architectural planning. But if the house is just standard and the floor plan needs major changes, then it quickly becomes very expensive without resulting in anything nice. If you just want to live there, you can insulate the roof, replace windows, and lay a few more cables. You can have the water tested, but in the cities there are plenty of rental buildings that function well with 100-year-old pipes. If you want something quickly nice and modern, and don't have around 250,000 lying around, then this is not your property.