Floor plan feedback: Semi-detached house for a 4-person family, self-designed

So first of all, I would like to distance myself from the manner of some previous speakers. If you are sure that an open space as a rectangle without an L-shape works, then go ahead. The dangers of sound, furnishing, and the like have already been discussed sufficiently. I would like to turn the focus to hallways and stairs. Every floor plan starts with that, and you have chosen the largest and perhaps not the most sensible option at this point. To anticipate, I also love half stairs with a landing and initially tried by all means to integrate them into our floor plan. However, I believe that this type of staircase makes many things more difficult. On the ground floor you have 16 sqm hallway plus 5 sqm staircase. So 20% of your area is circulation space. Upstairs it looks not much better with 11 sqm hallway, 10 sqm airspace, and staircase. Here too, over 20% of your area is not usable for you. The walk to the utility room & shower bath is very long and far. I join my predecessors in their concerns about the costs and therefore suggest the following: Maybe reconsider the floor area you want to renovate and try to connect the levels with a centrally located staircase and small hallways. This saves space, enormously protects the budget, and in no way limits your living space and thus the luxury you want to treat yourself to. I have the feeling you are still at the beginning of your considerations and from my experience, it is not bad to let go of some ideas, above all a certain staircase, because it becomes the central element in the house and should therefore be 100% focused on efficiency. Good luck with the further planning.