Total bathroom renewal

Current bathroom was built in 1989 and (probably) because of that it stands on a higher level compared to the rooms and corridor floors. There is a room next to the bathroom that we would like to increase the area. This bathroom does not have any windows, therefore it has dedicated tubes and ventilated chimine. In attached to the bethroom there is a storage room with a washing machine (so it contains water and drain pipes). Total area of bathroom is 12sq meters and storage room 4sq. Meters. This batchroom stays next to the stairs that goes to the 1st floor, therefore we can use some area below the stairs. What we would like to be done: Bring the bathroom floor to a lower level and rebuild the walls so that we can use some of its current area for the room. This will demand that some area of the bathroom needs to be shifted to the storage room and storage room can now be placed under the stairs. In summary, we would like to build a new storage room, shift the bathroom and give some of the current bathroom area to the room. Total of walls need to be rebuild, water, electricity and drains need to be shifted a couple of meters. We will then want tiles on the whole bathroom, a shower area and new ceramics.