Narrow plot with boundary construction - Various questions / problems

The barn has a width of 7 meters and a length of 14. Our "house" also has a width of 7 meters but is 12 meters long. The existing building may be expanded without any problem (!), if it is demolished, the entire wall must be a fire wall, no ifs or buts. Also without windows. The neighbors have only expanded their former barn and definitely do not have a fire wall (not plastered on our side, etc.). If we build the house as planned, only one house will border our new house, namely the house that is newly built. On the other side would be the neighbors' garden.

Too bad. For us, it was also about new buildings and would be a solution. Went from barn to house without permission.

Firewalls always have no windows.

I'm curious how the house will be designed. It's something completely different.

One could build a window there, however, a building encumbrance would be registered stating that the neighbors may never build within 5 meters around the window. And no one does that, I wouldn't do it either.

We can also convert the barn, but the walls are so dilapidated that everything has to be redone, unfortunately.

We would not have agreed to that either.

By chance, we still have more distance.

Have you ever talked to the neighbors. Normally, houses are built close to the street

The houses here are all positioned differently. We are allowed to build as far back as the house next to the neighbors (one house further) and that is about 25m away from the street. Both neighbors have agreed, especially since the new neighbors also have to ask us regarding boundary construction, so we have the upper hand.