Floor plan planning of an old building from the 1930s

Edit: By the way, the extension doesn't look nearly as bad in reality as it does in the pictures. The only thing is that the roof is really ugly, and the expert also said that, given the year of construction, one has to assume it contains asbestos.

I would redo the roof and adapt it to the old building as a curved gable roof. You would even gain some attic space.

What I also wonder: You are currently three people, right? What do you want with such a huge bunker? Even if you redesign it very generously, it is simply a lot of space to maintain and pay for. This applies even more to the property. As rightly says, it is a lifetime task to maintain it.

If you want to create a botanical garden, then certainly. At that size, I would design it like a park. High-stem trees, large bushes, and lawn. Large greenspaces are low-maintenance and the lawn is mowed by the robotic mower. Maintenance effort close to zero. If desired, you can create a small ornamental garden by the house. The maintenance effort there can be configured as desired.

If you want to create a botanical garden, then certainly.
Given the size, I would design it like a park. High-stem trees, large bushes, and meadow. Large greenery is low-maintenance and the mower robot cuts the meadow. Maintenance effort close to zero.
If desired, you can create a small ornamental garden near the house. The maintenance effort there can be configured as you wish.

Yep, that's exactly how we had thought about it.
The parts of the property that are farther from the house are meadow surrounded by fruit trees and bushes/shrubs. There's already a lot growing there.
And I don't even have to mow it that often. Bees and insects are very happy about it when there are still some meadows where the robot doesn't always drive over.

I can very well understand your enthusiasm for this old gem, I think these old houses have so much more soul than the new building blocks and I also felt a bit sorry to have to tear down the tiny settlement house that stood on our property (it still had such a wonderfully old entrance with glass, an old curved wooden staircase, and beaver tail tiles). But this particular property would intimidate me a bit if I didn't a) have a very high budget and b) have some experts on my side who are knowledgeable about energy-efficient renovation, conversion, and building damage. In your area, the prices for craftsmen might not yet be as high as generally in Bavaria, but before a potential purchase I would inform myself very carefully about what you might have to expect in the worst case and what subsidies might be available (mold? pollutant removal? unstable masonry and unusable pipes?) and also get an offer before any considered demolition. We had a really tiny house to tear down but just the asbestos disposal quickly drove the bill up due to hazardous waste disposal. I find the plot itself with this wonderful garden super beautiful regardless of the house (like you, I think of orchard meadows and in my case sheep that I would put on it with so much space) but since I am just as sensitive to noise as you described, I would reconsider this street, at my parents' place it looked similar at the time of purchase, now trucks drive through every 5 minutes and my mom is having a breakdown :)

I think these old houses have so much more soul than the new block buildings and I also felt a bit sorry to have to tear down the tiny settlement house that stood on our property (it still had such a wonderfully old house entrance with glass, an old curved wooden staircase and beaver tail tiles).

And yet you tore it down and didn’t dismantle it and reuse parts?

And yet you tore it down instead of dismantling it and reusing parts of it?

I’m not quite sure what you mean by that, you can hardly put an old staircase into a new floor plan, keep a glass entrance and attach it to a new building or integrate some beaver tail tiles into a new roof made of wavy tiles because that is unaffordable nowadays :) But if you mean why we didn’t strip it down: the little house was a total of 76m2 and I don’t like extensions to old houses, they always seem very haphazard to me :)