I have given my honest feedback and opinion.
1) Exactly, there is indeed no door planned. It wouldn't fit there. And beyond that, I also consider the hallway wasted space. There should be enough room for a small wardrobe and a bench. The space is sufficient for that. The door itself should be quite bright through the window and a large glass element beside the door on the ground floor. Upstairs we are still considering installing a window. But it wouldn't bother me without it either.
If a door "doesn't fit" there, it should be planned so that it does fit. Why would you willfully block yourself? We currently have no door from the hallway to the living area because the steel is missing. After cooking, you can still smell it in the upstairs hallway for half a day. Simply because the ventilation isn't designed for excess airflow areas and so on. I can only advise against that.
The sound issue adds to that. Watching a movie in the evening and the kids are supposed to sleep? Guests and kids going to bed? They hear every word. In the morning, the coffee grinder goes straight into everyone’s eardrums.
2) The space lovingly called "dead-end" by you in the bedroom was what we wanted. We also had a floor plan where the office (in a different position) was, but that made all rooms upstairs look small. This way I have a wide sightline and the room there (8m2) can also be separated later as an office. Before that, it is supposed to serve as a sports corner. A walk-in closet or something similar would of course also be possible.
Restart with a clear needs analysis and don’t sugarcoat makeshift solutions. It didn’t fit, "dead-end" is also OK. If you need a separate room, then build one. How do you imagine the office and home office situation if, for example, someone is sick and has to stay in bed?
3) As far as I know, the interior walls are made of aerated concrete.
That would basically be unacceptable to me.
4) Not quite, house costs are around 300k + additional building costs, but ultimately, of course, it doesn’t matter. It’s a lot of money. I would have had no idea where else the chimney should go so that it stands in a sensible place on the ground floor. That’s my problem. The development plan specifies that the chimney can only run along the central axes of the roof. (something about the maximum height sticking out).
Then that belongs properly planned into a room concept on all levels and not shrugged off with "it will work somehow." That’s why you build! If this were a renovation of a 1930s old building, I'd understand. But like this, when you have all the reins in your hands?
5) If this case should occur, I tell our guest that they’re welcome to poop upstairs. Then they can have peace the second time with excess sharpness (spice).
You don’t put a toilet next to the cooking surface. Period. You must have special fetishes to have no objective or subjective reasons against or to allow that. And so you probably don’t really like people either, right? If I need to poop at friends’ houses, I go to the toilet. Period. I don’t ask where it is upstairs when it gets serious. That will lead to uncomfortable situations that can be so easily avoided now.
Overall, you certainly won’t be able to create a floor plan that perfectly connects everything. That’s why I also said “No big deal.” Because compromises will have to be made in any case.
If that is the ambition, the result can certainly be sugarcoated. Keep going. Even for only 300k, you should bring more ambition in my opinion.