Hello, I would like to show you my propose, I hope you'll like.
DESIGN
I designed four apartments with similar conditions, everyone has an integrated living-dining-kitchen area and a private zone where there are the bathroom and bedroom. I tried that every unit has its own private open balcony without views from the other apartment, and is possible to get out from the social area, and in one case (apartment 4) even from the bedroom.
Every Living-Dining Room has a great space, you can install a six-person table, a sofa, a "puff" and you can walk around without any problem, there is a desk area close to the living too.
The kitchens have a great dimension and are possible to install all the devices (Refrigerator, oven, stove, washing machine, and more) and it's open to the social area to increase the real dimensions, the ceiling is lower than living-dining to generate a division between the areas.
The bathrooms have all the equipment needed, I decided to design them in an optimal way leaving more space to the other areas.
The bedrooms have 14 square meters, you can put a double bed, a tv, and a closet into the room.

CONSTRUCTION
I took a decision that I understand is very recommendable to increase the apartments quality, the dimensions, space, and if you want to rent or sold them they will have a higher value. I think that is necessary to build over the existed terrace, 20sqm approx. and you will get a new space for apartment n° 4 and a balcony for apartment n°3, to do that you'll have to demolish a part of external walls 3m long approx. A good solution for that it could be using an INP16 steel beam. Even you can build apartment 1-2-3 and then build the last apartment.
I changed a few windows positions and I have to design new windows to get more natural light and ventilation.
You can see these changes in the P4, at the same time you can look wich walls have to build and demolish.
The kitchens and bathrooms positions have been thought to optimize the sewage drain pipes using the existing pipes.
I hope you'll like the project and can value the apartments design, I tried to do the best job for you, with a very low investment and a few changes over the existing walls you will get a great benefit.
I am available for every question or suggestion.
Regards.
Arq. Ignacio Mascolo