Floor plan for a single-family house with a basement on a hillside

That's just how basements are, right?

Basements are one thing, lowering basements by almost half a floor is another topic altogether.

What kind of iron rod is that near the driveway?

That is probably a surveying point (for the surveying itself, the relevant reference point is separately marked here).

If the manhole cover is the reference point, what is it supposed to represent?

Probably for the eaves and ridge height information of the properties, for which it is closer than one of its peers. So also for the OP’s property, for the neighbor on the left side then the other one.

Are these 10x 29.5cm height?

I believe that was told to us exactly like that.

Name the development plan. With such selective information, you can do little.

I don’t have much more info on that. What information is missing?

In my opinion, the garage/carport belongs on the east boundary, since there you already get 1.11m higher. Placing the house as close to the street as possible also helps reduce costs. Likewise, planning the house to be narrow.

I also somehow like the idea of the garage/carport in the east. We had it in the west because we wanted a balcony there. But we need to reconsider that. The advantage with the height difference is certainly not to be underestimated.

Probably for the eaves and ridge height specifications of the plots, which he is closer to than one of his colleagues. So also for that of the OP, for the neighbor to the left then the other.

Where can I get the requirements for the eaves and ridge heights? Is that actually stated in the development plan?

I don't have much more information there. What information is missing?

As I said: "Just name the development plan."

Where do I get the requirements for the eaves and ridge height? Is that actually also stated in the development plan?

Yes. Possibly not in the drawing section; sometimes the "textual stipulations" are a separate document.