New construction 166 sqm / 1.5 floors / floor plan for a family of 5

It doesn't matter which way the table is oriented, these sliding door partitions require quite a bit of space in a kitchen because the standing wall sections have to be circled around and the corresponding distance to an island (if desired) is often not available.

Also, I can't imagine that this door is often closed with 5 people.

That's true, hinged doors are easier to move than sliding doors.

Yes, these universally popular super large window surfaces, and then also facing south, are a nightmare in summer. You mostly end up sitting in semi-darkness. Large windows, yes, but in the right place. Very few have a view that benefits from these window surfaces. Someone once wrote, everything else you see is the son’s tractor, the swing, sandbox, and garden furniture.

The shower bathroom on the ground floor would be too small as a parents' bathroom for me. The bathroom upstairs is used by the children, so there is no more space for the parents there.

Best regards
Sabine

Thanks to ypg for the template )

Thank you for your attention

So, the garage, the entrance, and the utility room are deliberately placed in the north. The kitchen and dining/living room should have access to the garden in the east.

Your mentioned bedroom has the best location on the plot. I would place the multi-purpose room, whether open or not, towards the southwest, the bedroom in the east, utility room northeast. Or something like that. Advantage: the multipurpose room also gets natural light in the afternoon during the darker season. So just reverse the house.

Actually, I forgot to mention that my concern is purely the evaluation of the floor plans and not the depicted furnishing.

The actual furnishing is important for the assessment: here you can see that the sliding door could cause problems when visitors come, the wardrobe is after all only a coat hook, and the bathroom on the ground floor is insufficient.

We are still uncertain about the following points:

1. Whether the large kitchen window (door) should remain or give way to a narrower one!?
2. Whether the kitchen remains open or semi-open with sliding doors as in the drawing.

Have you ever thought about separating the living room?
And regarding the kitchen furnishing: island or not? As drawn or differently?

3. The staircase is currently planned to be closed in order to create a small storage room/pantry underneath.
Here the cost/benefit ratio matters. Whether the certainly quite small gain in space is worth the 2,000 EUR extra charge!?

Do it! Where will you put your shoes and jackets? Without a wall or chamber under the stairs, it's hardly feasible.

The wardrobe simply represents space for hanging hooks and shoe storage. That’s why it’s around the corner, so that all the clutter disappears from the direct view of the entrance area.

Hmm... it’s not quite “out of sight” at the moment, since the bedroom is almost directly opposite.
As I already said: arrange the living room, dining, and kitchen more towards the southwest instead of southeast. I see the terrace around the corner, but more to the south.
You will hardly enjoy the guest WC or the parents’ bathroom: it will be quite tight and uncomfortable. You will rather use the stairs and the upstairs bathroom.
For me, I would then conclude to juggle the rooms again. Conservatively, I rather see the bedroom on the sleeping floor than a hobby-office room. The children must keep order disciplined anyway, and I see home office rather separated from the children’s room.
Anyway: I would probably make an open plan kitchen here or include the living room with it. But then separate the hobby room from the multipurpose room and somehow include or use it. That makes more sense to me than the bedroom with emergency shower on the ground floor.

Do it! Where to put your shoes and jackets? Without a wall or a cupboard under the stairs, hardly feasible.

Yes, in this case the wardrobe is housed more conveniently here than a pantry.

The design is well structured, successful, and compact. In my view, it is not meaningful to evaluate it without furnishing. The house is a shell for your life. "Traffic routes" and space for everyone already play a role here. Especially with compact room dimensions, it is crucial how furniture, space, light, and movement fit together.

1. Whether the large kitchen window (door) should remain or be replaced by a narrower one!?

If you use this door often and, for example, have an herb garden in front of it or can imagine an unofficial "children's play entrance": wide.

2. Whether the kitchen should be open or remain "semi-open" with sliding doors as in the drawing.

We like it open. But that means nothing for you. I see the advantage in the more spacious feeling in the living area.

3. The staircase is currently planned as closed to create a small storage room/pantry underneath.
Here, cost-benefit ratio is the question. Whether the certainly rather small space gain is worth the 2,000 EUR extra!?

It is worth it. Less work (cleaning under an open staircase is annoying) and a dust-free usable space. 2,000 EUR is okay for a "custom built-in furniture" – you can really spend money more foolishly.