Development plan - Is it possible to enlarge the living area?

Here you will get help

Attached is the floor plan - unfortunately I don't have a better one. And also the calculation of the usable area
Unfortunately nothing with dimensions. Roof is... slanted? Oo I think 40 or 45°, at least according to the development plan.
The attic will be converted, but since we want 2x office + 1x hobby, there is a lack of space.

The old owner gave away valuable GF.

The old owner gave away valuable GF. only 11.5 * 10.5 m instead of 13.0 * 11.0 m

I unfortunately don't understand that now? How do you see it?

He only used 11.5 m of the possible 16 m. In width, also only 10 or 10.5, it can't be determined exactly with the plans.

Here again for better visualization. The blue marked areas are used.

If I googled correctly, building boundary. 2 lines, 1 dot?

Building boundary. Ok. Stupid.

Edit: I just saw on Google Maps that the building north probably already deviates from the plan,

Now I have blacked out everything so diligently, and now the address is then especially visible on the calculation :-/

I wanted to politely ask if you could show the Google Maps, but this way is good too ;) They surely won’t buy from you :)

They probably won’t be illegal buildings,

Why not? A co-owner who doesn’t inform himself just builds a conservatory, everything is fine.

Does the roof have a knee wall? Roof pitch???

It is a single-story, so 3/4 or 2/3 of the attic as living space.

I see the wasted living space the same way. He built a large double garage there where living space could actually still be generated nicely. So I would consider converting the garage into living space during the renovation work. Upstairs the attic can be done the same way. And further, the terrace behind the double garage could also be extended as living space.

Phew, the price is amazing.. The neighbor to the north has built an extension, but ancillary rooms/garages (no living spaces) with boundary development. That is apparently allowed.