Plot found but too big - Seeking construction partner

We are only buying the front part. The back part is being purchased by another partner. We have nothing to do with that. However, this partner only wanted to buy if construction is possible and the seller wanted to sell both parts. Ergo, we can only buy if the one in the back can build.

A few new pieces of information. According to the lower building authority, development of both parcels is possible without problems with one single-family house each. Should the municipality cause trouble, according to Brandenburg Building Code §71, a substitute measure will be carried out by the building authority. Statement from the planner who will probably plan the house and is also located in [KW] or has very good contacts with the building authority caseworker, also zero problem, it will work, has discussed it with the building authority. Eichwalde actually doesn’t want a second row, but the district wants more residents, so it has been mandated by the head of the building authority to allow a second row.

If the municipality does not cooperate, a substitute action will be taken by the building authority in accordance with Brandenburg Building Code §71.
Statement from the planner who will probably design the house and is also located in KW or has very good contacts with the building authority officer, also zero problem, it will work, has discussed it with the building authority.
Eichwalde actually does not want a second row, but the district wants more inhabitants, therefore it is mandated by the head of the building authority to allow a second row.

That sounds to me like macho talk from your planner. A building permit will probably ultimately be granted by the district, and this is indeed not bound by the vote of the municipal building office but can also conduct its own review and reject or override it. The legal basis of the building permit remains the planning intent, for which the municipal level is responsible. If there is no development plan, §34 of the Building Code does not automatically have to take its place alone. The district can thus only approve your building application per ordre du mufti if the municipality has failed to record its intent "no second row" in a local statute. The subsidiarity principle also applies in Brandenburg, i.e. the municipality is responsible for a development plan (or equivalents such as a design statute, alignment line regulations, or the like).

Since there are already several houses in the 2nd row, see above, it is highly unlikely that such a local ordinance exists. But as already mentioned, we are only partially involved. Our house will be in the front, where construction is definitely allowed; according to the majority opinion of the planners and the mentioned office, it is also possible in the back.

Our house will be at the front, where construction is definitely possible; according to the majority of the planners and the mentioned authority, it is also possible at the back.

A house initially approved "at the back" is then (like the existing building) the "first row" and can block that another one be built between it and the street.

Since there are already several houses in the second row, see above, it is highly unlikely that such a local statute exists.

One may have been created after these. An appeal to the principle of equal treatment requires that the case constellations are fully comparable and the regulatory framework has remained unchanged in the meantime.

I assume that a responsible clerk of the lower building supervision would know if there were such a local statute, wouldn’t they?

At least in the official announcements of the community, there is no local statute, so I assume that the community does not have a local statute and if I am legally correctly educated, then what the lower building authority says applies.