Hello, regarding the staircase: This is really one of the most difficult points. Back then, I needed a lot of time, also to find good information on the internet about the space requirements for different types of stairs. (Search term: staircase + space requirements) The exact size of the staircase also depends on the floor height. The floor height depends, for example, on the building materials (insulation of the floors, underfloor heating, construction of the floor slab, etc.) and on the construction company carrying out the work. For initial attempts, you can copy stairs from the floor plans of turnkey providers, but as mentioned, it might be wise to plan some buffer due to floor height and so on. Do you want to contract all trades yourselves? The staircase builder will also need information for this, but such a person could help you at first. You will need one anyway, so get a consultation first. Many staircase builders also have a showroom where you can see various staircases and options. That’s fun, and a lot depends on the staircase. By the way, you save circulation space on the upper floor if the staircase arrives there more in the middle and less at the edge. My idea for you: Since you can and want to afford a lot of living space, how about a straight staircase? This could lead directly opposite the front door (of course with sufficient distance). In the large dining/living area, you would have a kind of alcove above which the staircase would be hidden, in the room. There are several options for this alcove: simply as a room divider, with a triangular window (through which you can see from the sofa to the kitchen or so), with an aquarium (visible from both sides), hiding technology inside it (circulation pump), building a fireplace next to it, door or drawers with storage underneath, bookshelf... You have 6-7 meters depth in the living room, so you could easily afford that! Our living room is only 4 m deep behind the hallway; unfortunately, we couldn’t use this solution. But for your upper floor that would help, the circulation area could shift further to the left, all rooms on the left could move a bit away from the corridor shape towards a square. Rectangular rooms are great; I wouldn’t let anyone convince me otherwise! There is no easier and more flexible room shape to furnish. Square is best, but it’s just not possible for all rooms to be square. If you plan a straight staircase with 4 m and with 25 cm (less than 3.75 m would be uncomfortable) more or less fits your planning later, you can probably start with that in my opinion. Have fun P.S.: Idea: The technical room in the middle of the house, maybe on one side of the staircase? (For a wider living room upstairs without the proposed alcove.) Why give the technical room an exterior wall where every other room benefits much more from a window and a view? But that might only be possible if you don’t have a central controlled residential ventilation system and no heat pump.