ᐅ Idea for Dividing a Floor in a House

Hello everyone,

I am looking for ideas regarding the following matter.
I will be renovating a floor (130m2 (1400 sq ft)) in my grandparents' house.

Since we want to separate this floor, we are currently searching for the best way to do so.
The following points need to be considered:
- The separation should be placed before the entrance hall; the staircase must remain accessible, as there is a second floor.
- It should be mostly opaque for privacy but still allow light to pass through, as the only windows are in the staircase area (a balcony door and three large windows).
- It should be lockable with a door.

What would you recommend?
The height is 2.60m (8.5 ft), the width is 2.35m (7.7 ft).

Thanks in advance,

Best regards

The first and third points are understandable.
I don’t understand point 2. Do you perhaps have a drawing of the exterior and the floor plan of the stairwell?
If the third floor is being developed and the first and second floors remain for the grandparents, wouldn’t it be possible to add your separate entrance on any other side?

Best regards, Yvonne