Cover shaft 1.5 x 1.5 concrete like structure

What information is needed?

Dimensions 1.5 x 1.5 meters
An opening for the manhole cover must be included
Soil should be placed on top for flowers and/or just grass. The soil layer would then be max 10 cm

The existing wall is already described. Concrete block 25cm with 14mm reinforcement and fully poured.

Subsequent holes can be made by core drilling

What information is needed? Dimensions 1.5 x 1.5 meters (inside or outside?) Opening for manhole cover must be included (where, how big, which shape/) On top should be soil for flowers and/or just grass. Soil layer would then be max 10 cm (will there possibly be traffic loads like cars, trucks, excavators or something?) Existing wall is already described. Concrete block 25 cm with 14 mm reinforcement and fully poured. Subsequent holes can be made by core drilling

Is the pool really on top or only on the photo on top?

It borders directly there and is virtually located above it in a figurative sense. In general, there is no difference in height except that there are 30 higher pools above.

Here is the sketch, with optimized coverage. You have to make the plan yourself.

I would cut out the bearing pockets with the angle grinder, then chisel them out (possibly pre-drill with diamond core drilling). Then make the formwork. Then cast the cover (0.05*0.5m) and then place it as a stay-in-place formwork in the correct position on the formwork. The side formwork of the cover should be smooth. (Don't forget the release agent). Produce reinforcement with stirrups. A mesh is also possible, but then some additional supports like with the stirrups must be added.

Thank you for your information and the sketch. And simply reinforced with 10cm of concrete is actually enough here even with 8mm?

Intuitively, I would have doubled the reinforcement with at least 10mm and 20cm of concrete.

But I am also a scaredy-cat and like to over-dimension sometimes.

But if you say 8mm according to the sketch is enough with 10cm, then I'll do it that way. Steel prices are awesome *irony* at the moment.