Narrow plot with boundary construction - Various questions / problems

Garage is a good keyword.
Where else should it go with 7m width? Actually, it only works in front of the house, but that again takes away scarce window space.

Maybe you could post a site plan with a north arrow and the buildings of the neighboring properties. And then I read "Abriss" .. is that an existing building that you want to basically replace? Or is that in another location on the 7x90 m long property? Is there still access to the property from another point?

The existing plot has a width of seven meters and a length of approximately 90 meters.

That reads to me like a field that has never undergone a land readjustment. Does a neighbor also want to build on one of the sides? – then one could now start the readjustment, and one would get 45 m depth from the front road and the other from the back road. Post a cadastral excerpt, then one can brainstorm constructively. A floor plan with a towel aspect ratio forces unfavorable room arrangements and becomes a space eater because you have to add the area of the pearl necklace corridors. Too much depth leads to too much roof height. All of this sounds so unfavorable that alternative approaches suggest themselves. Without an architect, nothing (reasonable) works there. How is the development regulated: §34?

I would also like to see the site plan with the building envelope. There are several options: from the passageway in the house to the back or from the previously mentioned variant with [TK] and carport. With 7 meters, you can easily follow designs in the [RH] sector, but you also need to know how the floor area ratio/floor space index, how high, etc., you are allowed to build. I still have a great picture book with [RH]s somewhere on the shelf.

So, here is a site plan of the property. A brief explanation:

If you look at it, the right side has been completely demolished. The building where the A is (barn); the new house is supposed to go there. The front (towards the street) will also be demolished, but only after the new house is built, because we still live there. On the left there is another house that will remain. We are building about 2 meters in front of the other house (hope you understand what I mean).

At the front by the street are parking spaces and behind them a garage.

The house basically has no direct house as a "neighbor" on the left side. On the right, the new house (which still has to be built) will directly adjoin our house.

In another thread here I addressed the topic of fire protection walls again because there is §30 in the state building regulations of Rhineland-Palatinate that states that no combustible materials are allowed in a fire wall. The prefabricated house manufacturers say, "yes, you are allowed to"...

Does the fire protection wall really have to be built along the entire length? It would already help if it were only 7 or 8 meters.

With us and our neighbor, it is regulated as follows. The neighbor has boundary construction in the old building stock, with us the old building stock is partly boundary construction, partly the boundary distance is correct. Solution: Where the old building stock has boundary construction, the new building may also be built on the boundary. The rest must observe their distances. The neighbor built first and had to partly execute the wall as a fire protection wall.

I would look for an architect who has experience with infill construction.