Looking for information on basements with a white tank

Since you mention both in the OP: of course you first have to decide whether you want [Lichthöfe] or [Lichtschächte] – as [hanghaus2023] shows, a [Lichthof] would be the case, but obviously it cannot be waterproof against pressure.

Since you mention both in the OP: of course you first have to decide whether you want light courts or light wells – as hanghaus2023 shows, a light court would be what, but of course it cannot be watertight against pressure water.

The one in the picture, as you correctly recognized, is not watertight against pressure water. However, no water enters. The drainage is deeper than the light well so that no groundwater can penetrate. The drainage is only for rainwater and is connected to the house drainage system, so that in case of a backup of the roof drainage, water from the roof does not rise into the light court. It is possible to integrate the light court into the wastewater system. However, this becomes very complex. First, see how high the water level stands.

As previously written, first wait for the soil survey. Based on the existing borehole profile, there is no free groundwater. The design water level is then assumed to be the ground surface level. The water issue arises from temporarily accumulating seepage water. The soil is weakly permeable, and the water collects in the backfill area of the basement. Theoretically, this should be controllable with drainage. That needs to be assessed once the survey is available. For prefabricated houses (wood frame), a geotechnical measure for uplift safety is required anyway in case of water accumulation (I don't know if this is the case for all manufacturers). In any case, a ring relief pipe (aka drainage) would need to be installed (depending on the basement’s embedment depth).

I would first consider whether it might be better to build the house on the basement.

No, I consider the phrasing (Freudian slip?) "to build the basement under the house" to be accurate insofar as the decision for a favorite house model (against all wise procedure!!!) has apparently already been made. But of course, it would be advisable otherwise. We will see what willingness to gain insights is present.

Here is another picture LS with drainage

wow great thanks! Where does it lead to then? Sewage? Cistern?

I would first consider whether it might be better to build the house on top of the basement. Otherwise, first wait for the soil report. If the basement is absolutely necessary, then your planner should know what he is doing. The spoiler should be particularly noted!

My wording was a bit awkward on my part. Of course, we want to build the basement first and then the house on top of it.