-Italian version in the drawings-
The solution tries to optimize in the better way the spaces. The aim is to create a big living room that can be flexible for whatever function it will be use. The kitchen lay the new wall shared with the bathroom. There are 3 windows: the two smallest ones and the thin and large one upon. The bathroom has the standard fixture and a small space to place the boiler and the wash-machine (that can be placed also among the kitchen's furniture). You can choose to keep the couch and the shelving unit or to use this space as meeting area and split this area from that used for services (kitchen and bathroom) with a drywall and concrete glass. The mezzanine is accessible from a prefabricated stair, that it can be bought by a bricolage shop. The mezzanine is the sleeping area: it has a bed as a futon, the shelving unit and a darken curtain. This is the most dark area of the house, because of this can be used a wall light or a floor lamp (see renders). This lighting solution can be used also for the other spaces of the house. From a structural point of view, the works are not invasive: can be used the existing hole for the metal beams, moreover the two walls sticking out can be forced with two parallel walls.
From a plumbing point of view, the new water pipes can be realized in the new wall (the one between the kitchen and the bathroom). The heating system can be realized under the floor or with the external heating elements (see the demolition/construction plan, the heatings elements can be placed where the asterisks are placed).