Draft floor plan of a single-family house (convertible to a two-family house in old age) on a slope

What exactly? A bullet point list or something similar would be helpful.

Is the question serious? You've been around here for half a year already. The "highlight" is sleeping. In general and especially the upper floor: You can't reasonably fit the number of rooms into the few square meters – as one (actually) can easily see. :rolleyes:

The "highlight" is sleeping.

This is the guest bedroom...

What is to be divided later and under what conditions?

If parents sleep there, they get access to the garden
The living area gets the terrace
actually makes no sense
What is the conservatory for?
How is it accessible on the upper floor or is it open?

Please draw the desired furnishing on the ground floor to scale. The dining area seems much too small, plus the dead space between dining and cooking.
Closet is missing on the ground floor

What is supposed to be separated later and under what conditions?

The upper floor is to be separated as a granny flat once the children have left the house. For this, a drywall partition will be built at the north entrance of the house and that’s it. Then the apartment upstairs is separate.

Parents' bedroom gets garden access
Living room gets the terrace
doesn’t really make sense

Why not? The area south of the parents' bedroom is a steep slope of about 30°-40° (downwards), so it’s more of a utility garden than anything else...

What is the conservatory for?
How is it accessible on the upper floor or is it open?

It’s not accessible upstairs; it’s an open space.

The dining area seems way too small, and also the dead space between dining and kitchen

The dining table is 1.4m by 1.2m and that’s not dead space but un-furnished freedom :p

Cloakroom missing on the ground floor

In the first post about the new floor plan, I tried to explain that at the east entrance there is either a storage room or cloakroom. Probably more likely a cloakroom; unfortunately, both don’t fit...

The drawn table is not 1.2 x 1.4 m. The minimum space requirement for the dimensions is 2.8 x 3 m. However, no one can pass by comfortably when the chairs are occupied.

Freedom in that spot?

Which entrance will be your main entrance? That is where jackets and shoes belong.
How big are your children, actually?
Are you already planning the technology for 2 housing units?

How do you get to your terrace on the ground floor? Only through the narrow window in the "conservatory"? And how is it supposed to be furnished so that a passage is still possible? And why does the conservatory have a continuous wall to the hallway/dining area?