Site planning and floor plan - Your assessment wanted

This is the dimension where you can still sit at the head of the bed when the headboard is under the slope. Everything else restricts too much, even in the children's room or bathroom.

Slowly we are repeating ourselves

Again about the carport:

How is the protection against frost etc. there? Our driveway is on the west side. So it will definitely be open on that side. Currently, the plan is to eventually build an intermediate wall only on the garden side. Possibly also an end wall. Are 1 or 2 intermediate walls enough to provide sufficient protection? As mentioned, the west side will definitely be open. I don't want to put up a 10,000 EUR carport and still have to scrape in winter.

No one can tell you that for sure. It depends on the climate conditions, the surroundings (e.g., river nearby because fog often forms there), etc.

Here with us (carport with a wall to the south and partially to the north) you do have to scrape in the deep winter (if there is any), but it's much easier.

At least here in the North, a carport doesn’t need any walls so that you don’t have to scrape.

Okay, it probably makes sense to take a closer look / listen around in the new neighborhood.

Topic floor area ratio:
We have a floor area ratio of 0.4. So we are allowed to develop
[522m² x 0,4] -> floor area ratio I = 209m²

If I understand § 19 of the Land Use Ordinance correctly, the driveway, carport area, shed, and footpaths also count towards the development. With these things, the floor area ratio may be exceeded by 50%.
Floor area ratio I x 1.5 = floor area ratio II = 314m²

If our house floor area remains at 10.5 x 9.5 = 100m², we are allowed to develop another 214m² for all the "ancillary facilities", right?

What about a terrace? Is it taken into account? If yes, at what point? I can’t find any clear information about this on Google...

The terrace belongs to the floor area ratio l according to my knowledge... however, I cannot imagine that it would not be approved if it would be tight with the floor area ratio l.