Central ventilation system is probably too expensive.
I would see this as a prerequisite, unless you have actually dealt with the topic of ventilation. In that case, I would rather prioritize the garage issue lower.
In the bedroom and K1 additionally an air conditioner.
Great decision, but there should still be enough capacity for one more device in the open-plan living area.
The indicated furnishings are currently the best idea,
You should first know your furniture exactly or clarify where you want to sit/lie, and then plan the rooms accordingly; for that, exact furniture measurements are indispensable. The dining area will be very tight anyway; this is noticeable even without measurements, especially compared to the kitchen, which is quite large. And then a fireplace plus a FHB? And do you really want to sit like that on the sofa in the living room with all residents, watching TV only straight ahead? A parapet height of 75 cm at the head wall of the bed on the ground floor also seems hardly sensible to me; the windows at the dining table cannot be opened as indicated. Open-plan living area rather small, hallway huge with an outward-opening door.
Number of persons, age 3+1, 17-55+
What exactly does that mean?