Two full floors?

We are currently in negotiations to purchase a plot of land (Bavaria). Unfortunately, there is a development plan from 1962 that applies to this building gap. Accordingly, only construction with two full floors and a pitched roof (30 degrees) is permitted. A knee wall is not allowed. We would like to build a prefabricated house and have already looked at several options. However, for two-story houses that, according to the 2/3 rule, legally have two full floors, there is often talk of a knee wall. The highest I have seen there so far was two meters. How high would the walls on the upper floor have to be so that they are not considered a knee wall? And does anyone perhaps have experience with whether the authorities can be negotiated down on this matter? Thank you very much

Accordingly, only development with two full floors, gable roof (30 degrees) is possible.

That's nice, why don't you get such a house offered (prefabricated house builder, solid house builder, ...)? :-)