Floor plan 165 m² with basement, your opinion?

I don't like the entrance through the kitchen. Do you really want a corner bench? I would leave out the pantry. You have a basement anyway. You like the separation between living and dining; I somehow see a lot of space that is only used as circulation area. I would leave the upper floor as it is. I would go to the basement from the hallway and go upstairs from the living room. Where have you planned the terrace? I am a fan of the kitchen being connected to the terrace.

The terrace is planned exactly between the living room and corner bench along the entire side (it is also the south side).

The terrace is planned exactly between the living room and the corner bench along the entire side (which is also the south side)

I thought so. You know that means sand dunes all the way to the kitchen.
For short distances and practical reasons, the path from the kitchen to the dining area (outside) should be just as short as the dining area (inside).

Draw all existing and desired furniture to scale. That's the easiest way to notice where it works for you. Does the shoe collection fit in the wardrobe, the books in the living room, the oversized bed, etc.

What do you mean by too short? Or rather, where would you say there is too little space?

Between the stairs and the terrace door. Technically plenty wide as a passage, but architecturally the proper narrow alley for Landvogt Gessler. In terms of spatial feeling, the living room here is in Siberia. Build YOUR house - separate yourself from copying the model house.

Reminds me a bit of ours.

"a bit" is also ours ;)

We carry dirty things like car tires etc. down the outside stairs.

Yep, I didn’t see those at first at all. And if the hobby room and co are down there, well then that’s basically right in the living and dining area, your strongest traffic area...
I don’t know if you are aware that four people who somehow still keep everything in the basement (laundry, hobby room, decorations here and crafts there, then the handyman), this hallway-... uh... living space is basically a little pigeon hole.

We thought we want the staircase in the anteroom due to the acoustics.

The acoustics may even be secondary then. Think about it – a general statement whether good or bad doesn’t exist here. About acoustics: with such openness you should consider another upper floor layout where you can separate something.

But we are still thinking about whether it fits that way or if we go from the living area to the upper floor or not. I thought maybe someone has experience with exactly such a problem

We have the stairs without a basement from the living area. But for us that’s no problem, exactly as desired. However: we have openness, meaning an open staircase and no kids. With us, nobody has to rush past somewhere, annoy or whatever. What bothers me about your idea is this massive central installation for this staircase. You surely plan it closed? And that would be, in my opinion, somewhat toxic for an open living concept. That doesn’t fit together. If you have a central staircase that affects almost all rooms, you also have to think about the optics, acoustics, and privacy. And I wonder if you took the former into account, that it just looks completely different when it’s a closed staircase.
What bothers me most about the stairs is the line of sight from the entrance to the stairs: it is basically not existing, completely ignored and feels wrong because it’s offset.
There may be those who can’t relate to that, but such a thing makes the difference between a DIY floor plan and a professional one.

After subtracting the tall cabinets, only about 1 meter remains as a passage. I think a few centimeters more wouldn’t hurt here. Often, at least 1.1–1.2 m is recommended.

I wouldn’t turn the kitchen into a passage room at all: get rid of the pantry, but instead have a storage room accessible from the front where you can get the broom without disturbing the cook. Tupperware parties, card rounds and collective football TV then become a family affair.

I took a look at Regnauer. I’ll put it this way: the home builders put features in their show houses that have a wow and whoa effect. Some are damn expensive or just not everyday friendly. Instead of walls, they build none and generate amazement. These so equipped houses are supposed to make someone want to buy them. Then the client wants this house because of this wow effect, but the house is then cut from this effect for cost reasons. Or it’s reduced in size so that this and that can definitely still be realized. In the end a house comes out that still resembles the show house but is no longer the one. Exactly what makes it special is missing.
Yours is already a bit more everyday-suitable: cloakroom and kitchen can be used. You can also watch TV now, where one window was left out.
I don’t see that on the upper floor. Laundry chute in the bathroom, two windows in the bedroom, one of them still above the bed...

How much is all supposed to cost?

I would definitely have a shower, albeit a smaller one, in the WC on the ground floor; that little bit of space can be found, because who knows how your life or that of the roommates will change. The dining room situation should be drawn CONCRETELY with measurements, just as it is supposed to happen in your life. So far, there is a larger room between the kitchen and the living room, which I cannot imagine without your concretely drawn idea. For us, it will be similar with such a seemingly "pointless" free space in between, but we want it that way and know how we want to design/use it there. Similarly, I feel about the living room area by the window, which seems to me rather like a pure walking or passage area. Given the not exactly generous space of the open-plan area, I would look at that again, especially also regarding the staircase in the room. At the entrance, you should consider that the drawn car essentially drives right past the front door and thus reverses past it when leaving... it will be similar for us, so there is either a platform or a post of the entrance canopy there as a precaution.

But we are still considering whether this fits or whether we go from the living area to the upper floor or not. I thought maybe someone has experience with exactly such a problem

That is not a "problem" but merely a matter of preference. Sometimes it will bother you, then again you will be glad about it. It depends on many things: cooking, visitors, noise, etc.; I can imagine both. If integrated, then it must also appear as a unit in terms of design and not as a cold, wet anteroom, but part of the apartment. As long as the staircase stays as it is, I would also prefer to go upstairs from the terrace side and to the basement from the hallway. So far, I find it quite separating with a "narrow" passage and thus wasted space.

Here is the site plan to show the orientation.