Considerations regarding house purchase and the necessary renovation.

Hello! I am currently considering buying a house. It was built in the 1920s and has been well maintained since then. 2 floors + basement + converted attic, a total of 175 sqm. The condition is really very good. No damp walls/basement, doors/stairs/etc. regularly maintained,... Now there are some points where I am not sure whether they need to be done or not. Maybe you can help me assess the necessity and the costs needed for the following points:

-Oil heating - is 15 years old, renewal already necessary?
-Pipes run outside the walls
-> I would like to hide the pipes in the wall (if renewal makes sense).

-Windows - estimated age: 30 years. About 20 windows. Double-glazed, plastic frames. I actually want to replace them for aesthetic reasons, but it probably also makes sense energetically, right?

-Electrics - completely renewed 10 years ago

-Roof - 25 years old, tight, insulated and converted.

-Insulation/facade - no additional insulation so far, facade is in impeccable condition, replastered and painted about 10 years ago. I would like to avoid insulation for aesthetic reasons (beautiful old building details).

-Demolition of garages - There are a total of 5 garages on the property, of which I want to demolish 3 to gain garden space. They are individual prefabricated concrete garages. What does the demolition cost?

-Floors - mostly to be redone. Mix of tiles/wood. Total 175 sqm.

-Bathrooms - One bathroom can be kept, a new bathroom will be created in the current kitchen. Is it problematic in an old building to lay the necessary pipes?

-Renovation - New wallpaper is to be applied throughout the house.

-Floor plan - To be slightly changed in a few places. One interior wall is to be completely removed, at 2 places an existing door is to be widened so that the rooms are more "open" to each other.

I want to do all the work now that would come up in the next few years anyway, to have only one construction site. What is still okay now or can be easily improved later can wait accordingly.

Which work do you consider necessary? What costs can I expect? I have roughly estimated the following:

-New heating incl. pipes in the wall - 20,000€
-New bathroom - 10,000€
-New kitchen - 15,000€
-Reserve for roof (not to do for now as long as it is tight) - 30,000€
-Demolition of garages - 5,000€
-Window replacement - 20,000€
-Floors + wallpaper throughout the house - 10,000€
-Floor plan/wall work - 20,000€

That means I come to a total of 130,000€. Is that realistic? Have I overestimated somewhere? Have I forgotten something?

Thanks a lot in advance for your help!!

I am currently thinking about buying a house. It was built in the 20s and has been well maintained since then.

.. I know something like that ... before you see everything rosy and easy ... I can only advise you: find a good architect / construction manager or similar who is familiar with this matter and go through all the rooms on site point by point and create a very detailed scope of services including quantity calculations ... if the location and the property do not cover the value of the renovation ... keep away ... later there will be no one who will pay you back all these investments ...