Floor plan single-family house gable roof 1 full story 140 sqm

Ok, entrance from the front.

I hadn’t considered that aspect at all and it is justified. The problem is, the property received an entrance on the west side as part of the road renovation. Accordingly, it is of course obvious to install the carport there as well. That’s where the problem with the narrow property comes into play immensely. There simply is no space.

If you already make 10 meters of yard/front garden in the front, the carport fits there wonderfully.
And if not, then you can drive up on the west side and access the garage at a 90-degree angle. For example, we have exactly the opposite: entrance in the east, but the garage is positioned transversely in the west.

Cool how more and more regulations are popping up here.
So please post all necessary information here in the forum again.

The building line in the development plan is indicated as 10m.

Building line?
A building line obliges you to build up to it. I don't see that here. There are different possibilities.
A building envelope is limited at the front and back.
Here again an example of how the carport can be placed, although there is no problem regarding a normal extension on the south boundary.
Otherwise, I have to say that this is a bit too confusing for me - the information about the property comes only randomly. I'm just reading along now.

Building line?
A building line obligates you to build up to it. I don't see that here. There are different possibilities.
A building window is limited at the front and back.
Here again an example of how you can place the carport, but there is no problem regarding a normal extension on the south boundary anyway.
Otherwise, I have to say that this is a bit too confusing for me here - the information about the plot only comes by chance. I'm just reading along now.

Don’t be offended, it was mainly about evaluations and suggestions regarding the floor plans for me.
I would have liked to edit further information later in the initial post, but unfortunately that is not possible..

Your girlfriend should reconsider her priorities. Sounds harsh now, no offense intended.
Stairs need space.
Peninsula with closed kitchen
Doesn't fit into the house. It's a nice single-family house, not a villa.
A side entrance does not exclude a pretty front garden.
A house that feels spacious, bright, friendly, and offers the maximum living quality is more important than the fixed idea of a front garden.
A bit of creativity and you have a great, representative front garden with a side entrance.

The closed kitchens with islands in the magazines are great. Absolutely undisputed. Ideally with a large window front and a view of greenery. We also had that once in the plan. The rooms are large, the budget is not tight, function comes second.
The same with a large hallway, straight staircase. In your case, shoes, sports bag, and MaxiCosi are lying around in between.

Please draw the building line on the plot, the planned house and garage. I like Ypg's suggestion with the side entrance, west window, and elongated shape.

Regardless of how you decide, without a west-facing window in the living and dining area, you will not feel grounded because it is always dark in the evening. On our street, three of our neighbors and we have modernized houses from the 70s. And all of them have made window openings in the closed west walls because previously it was too dark with only south-facing windows.

One step missing? Are there guidelines that specify how many steps are needed to comfortably reach the next floor?

Yes, of course! There is a DIN standard for that. (How un-German of you not to know that. ) Just Google "Treppe 1x1", that is an online tool where you can calculate the stairs according to DIN. A floor plan always includes the entire property if done properly. This also includes parking spaces, vegetable beds, and also, for example, front gardens. I find the second floor plan quite usable, although the stair question still needs to be clarified. In my opinion, however, the entrance is too narrow – a wardrobe would only fit under the stairs or in the hallway, where everyone would trip over shoes. If the entrance is to remain there including a straight staircase, I would add a bay window / vestibule at the front. This expands the entrance area, relaxes the stair situation, and ideally creates a wardrobe space for shoes. Furthermore, it possibly highlights the beautiful front garden that the homeowner wishes for. I read open kitchen and kitchen island and see 2 conservatively closed kitchens? What now? An island only works where there is enough space for it. 2m width and 80cm depth are the dimensions I think it needs. Something like the protuberance in plan 1 wouldn’t be my thing, well, and 2 would save itself the furnishings right away because it would be difficult. West-facing windows are a must, even if the neighbor regularly dances naked in the garden there. Light finds its way around corners too. It’s not just about the view but mainly about letting light in. A terraced house feeling is not desirable. Exact details about building lines, building plots, or other boundaries make it easier for all readers. Overall, this is not a disaster approach but in my opinion still quite a way off from your dream house. The straight staircase dominates the house – how important is it to you?