House and garage - How best to place them on the properties?

I don't think they see it that strictly there. Actually not.

But sitting on the main terrace at the end of the property is something else.

With 9.45 it also works. However, I find the floor plan very questionable: everything looks very spacious with dollhouse furniture. But usually, you don't have dollhouse furniture, but other pieces. However, this is not about the floor plan here.
I don't like these standards anyway

One thing must be said. Even if you have already doubled your plot to 572m² with 2 plots, it is still a small plot to build a house on. And yes, with 300m² you only have a narrow strip around the house, which in my opinion does not deserve to be called a garden.

Please don’t misunderstand. Anyone who wants to build their house in Munich must already be a millionaire with 572m². This makes the land more valuable but ultimately not bigger.

9.45m x 10.45m is a suitable moderate house that is perfectly fine. But sitting on the property boundary or even lying in a bikini there surely won’t be any fun for the lady of the house.

I would strongly advise you to measure all your current furniture (beds, sofa, tables, etc.). Then take graph paper and draw this furniture into your floor plan.
In my opinion, you absolutely need a better sense of the dimensions so that you won’t be disappointed later.

We could also build a south terrace, that's not the case yet. We initially planned a terrace on the west side because we are mostly at home from the afternoon onwards and often sit on the terrace until late in the evening. On the south terrace, the house would cast a shadow and we couldn't sit in the sun. My wife's sister has it that way, and we don't like it that much.

Regarding furniture, you can see the different opinions that exist. We already find the layout very generous for us. On the ground floor, there would be a couch, lowboard, TV on the wall, 1-2 sideboards, dining area, and kitchen. I don't know where that would not be possible given the square meters and the layout.

The same applies to the upper floor. In our current rented apartment, we have a bedroom of about 16.5 sqm. There is a medium-sized wardrobe, a sideboard, a bed with nightstands, even the child's crib, TV on the wall, and we don't find it too small.

Then the children's rooms with 20 sqm would be a dream. I grew up with my brother in a room of about 15 sqm.

More and bigger is, of course, always possible. We could get a house with 200-250 sqm, but somewhere our budget is limited. We are already very proud that we can afford a detached single-family house of this size with such a large plot instead of living in a rented apartment all our lives. Nowadays, houses are often squeezed onto mini plots where you have no garden... THAT would not be for us. We would also feel comfortable in a semi-detached house with a sufficiently large garden, but since we can't afford that, we are building a detached house now.

Not everyone likes every floor plan, that is clear. We find the floor plan very nice. Maybe we will adjust something here or there, but overall, we like it.