Placement of house, terrace, carport & co. in the building window

Then the marked boundary in the south is almost correct.

You have a huge property, so you can safely move the house a bit towards the west.
Unless you want to divide the property later, then that is suboptimal.

My childhood home has a gable roof, I also somehow find that "cozy". What we find interesting about the townhouse is that you can place cabinets on all walls, including the exterior walls, even on the upper floor. I have also lived twice in architect-designed houses as a renter, I really like that, but I fear that the budget will not allow for something like that.

What does the strangely dotted line actually mean? Border to the green space? No designated building land?

I'm really curious about your floor plans.

What does the development in the surrounding area look like? Is there a cadastral map? Maybe check in [Geodata].

What does the weird dotted line actually mean? Boundary to the green area?

The vertically dotted line between green and orange is referred to as the "demarcation of different stipulations between or within building and other areas." The green part is designated as a green space, orange is an "other special area."

There is no neighboring development yet. I found a cadastral map online, but it does not yet show any subdivision of plots. The entire new development area is still one large parcel.

Then I hope for you that the green half was purchased at a better price.

So the southern plot can also be developed soon.

What is allowed to be built according to the [BB Plan]? Single-family house, semi-detached house, multi-family house?

More or less according to the standard land value, but that is fine given the plot size, the building envelope is really large enough. Detached houses with up to two residential units are permitted.