Please, let me tell few words, about the design.

- Shelves/ Closet, both sides, including small seating sofa place for taking on the shoes, with mirror above it.
Also, gyps wall should be placed to make difference beethween entering area and kitchen.
The wall which stays behind the wardrobe.

2-STEP STAIRS, entering the kithcen
There no more curved line, it is now one straight line, it is not big investment at all, but helps to make much more better internal organization.

Over the living area, are covered with thin wood surface

Is placed within the beams. I think it is the right place for your geometrical shape.
It is made of thin hexagone wood sticks and dark beige paper with light above it.

The wall right in front of the kitchen, facing the stairs, is covered wit dark brown or black chalkboard.
The place where you all could leave the massages for everyone! Everytime you move upside/ down, or going to
kitchen/ study room, you can draw something.

Is in the most silent part of the house, behind the kitchen. For entering the studyroom you should to pass trough the kitchen.
So, every time, your dady goes trough kitchen, he can kiss your mom!
Furthermore, they will be close to each other while working/ cooking. Second, if your father is cooking, it will not be an issue to make few steps to check the meal, if it is OK.

Dog unit, near the windows
Kid unit, under the stairs.
Spice unit, 2 levels, is bordering living area and kitchen, and there is a little plane to place your meal/ dishes, etc...
Plants, under the windows.
Book shelves, facing the walls.

Bathroom is open type, with glass beethween it and the room.
There is also a laundry room where you can place your washing and drying machines.
Behind the laundry room is the wardrobe closet room for all the stuffs from whole house, which you can not place anywhere.
The main wardrobe closet is located in the master bedroom, with its back on the wall.

I should keep all the current steel structure, and "just" covered it with gypsum plates and wooden hand rails on the top.
That is the safest and cheapest way, and even more, very elegance and clear.

A you can it is very very simple! So, you can enjoy your small garden, more stuff would just overcrowded the area.

I hope I made more clear, some stuff.
Have good time while building your dream home!