Narrow plot with narrow building window

Addition: This way you might be able to have a 5 meter wide strip for garden and terrace on the entire south side, of which 2 meters are covered. That would be my approach or goal.

Addition: This way you might be able to have a 5-meter-wide strip for garden and terrace on the entire south side, of which 2 meters are covered. That would be my approach or goal.

5 m on the south sounds tempting, but it would also mean that the house on the ground floor can only be a maximum of 4.6 m wide since I have the restriction from the neighbor to the north. After subtracting the exterior walls, less than 4 m remain. I think it will then become very elongated.

Then the garden could just be 4.50 wide and the ground floor 5.10 minus exterior walls? You could vary that a bit.