Large window front on the west side

All 50 building plots are available, only 25 are being allocated now.

Does that mean all 50 are up for selection, 25 applicants choose one, and the gaps go into the second round later?

Does that mean all 50 are available, 25 applicants choose one, and the remaining spots go to the second round?

That's exactly how it is

Does this mean that all 50 are available, 25 applicants choose one, and the vacancies go into the second round?

The municipality argued that the relatively small building authority cannot "manage" all 50 construction projects at the same time. When the first half of the building applications are processed and the first shells are standing, the rest will be next.

What I found out today... To the west, there will be a diversion for the surface water. Pipes will be laid underground and a drainage system constructed. Between the drainage (the green strip on the plan) and the building site, a protective earth embankment will be piled up - information from the building authority: 50-75 cm high. So far so good, I can live with the max 75 cm, but....
.... the earth embankment will be built ON the plots of land and a limited personal servitude for securing and maintenance will be registered in the land register :confused:.
I cannot explain why the municipality did not plan this earth embankment directly along the boundary behind the properties. Is this common practice?

The slope is present and drawn in the plan, if I am not mistaken.

Is that common?

Yes

I can't explain why the municipality did not plan this earth embankment directly at the boundary behind the properties.

Because there is no space there?! That is already the plot boundary. Distances must also be observed for objects in the area.
Be that as it may: not everything that others plan is explainable to you.
An alternative would have been: shortening all plots by 0.75 meters and hiring an external company or municipal workers once a year for maintenance. The requirement for the property buyer is simpler and more lucrative. Personally, I see no problem living with a small earth slope: you can simply plan it into the enclosure and plant it nicely.

Alternative would have been: shorten all plots by 0.75 meters

Yes, that's what I meant too. This earth embankment was already planned, I was also aware of that. At first, I was wondering how high it could be (the area is only now being developed). After the information from the building authority, I am relieved that it is only a maximum of 75cm. The height can be planned well, no problem. However, the entry in the land register makes me a bit suspicious. Are there really no significant disadvantages?

Is there really no significant disadvantage?

You are very likely obliged to maintain it. Anyone who has something at the edge of their property, whether a slope, hill, association ditch, or infiltration basin, is in some way obliged to care for it. This can also be the sidewalk in front of the property, the small strip of lawn...