NOTES
The apartment is big and its very comfortable so no need of rebuilding or demolition of walls (except in the kitchen as you like).
If you change the rooms orientations it will be expensive (thru wall demolitions).
So i leave the apartment as it is with furniture placement and made two variations.
1-Variation is with Bedroom next to bathroom and living room and the Studio next to bathroom (as it was in your plan) and the Kitchen with a lot of space with modern cook-table in the middle.
2-Variant i switch Studio and Bedroom so you have more space and light for studio room and bedroom will be next to other bedroom. In the Kitchen i put kitchen bar with (3) chairs.

About doors and windows and floor I suggest that you put new doors,windows and parquet. About the color i prefer light parquet for the floor (see photo) and darker color for doors and windows (all from wood) it will look really nice on white walls.