Basement waterproofing / Drainage for clay soil and brick foundation

Good day and a happy May 1st!

We have a problem with pressing water (layer water); a basement room was literally flooded because of it. Moisture has penetrated the masonry. Now we want to be "dry" in the future and are planning insulation/sealing of the basement exterior wall. For this, digging was done shovel by shovel, and lo and behold – it is the clay soil that stores and readily releases the water.

The facts are now:
We have already cleaned and plastered the wall and brick foundation (two bricks on top of each other) (multiple times with mortar and bitumen). After that, Styrodur boards were glued to the wall. Now the drainage system is still missing.

And now my question:

The exposed lower two bricks (which serve as the foundation) that also lie beneath a clay layer – should these simply be backfilled and tamped with soil/sand? Since a cavity has now formed there due to the gluing of the Styrodur boards. (see sketch)


Or what would be the best/further procedure regarding drainage preparation?

See sketch and photos.

I am very grateful for helpful tips and answers...

Kind regards
Rainer

The clay soil does not retain water. It prevents the water from percolating downwards.

Install a drainage pipe at the lowest point, connect the drainage to the sewer system, and cover the wall with dimpled membrane. Then surround the drainage area with gravel. Cover the gravel with geotextile (you can also completely wrap the gravel with fleece) and then fill with water-permeable material.

Thanks in advance for an answer.

But regarding my above question again:
How should the further process be with the cavity (for static and infiltration reasons)? Fill with sand/gravel? Or pre-glue with Styrofoam so that a drainage channel is created?

Clarify beforehand if and where the drainage may be connected, or if you fear "to wake sleeping dogs"

Caution when connecting the drainage to the sewer,
it is forbidden,
the basement floor level often requires a lifting system/pump,
when many do this, even with downpipes, basements tend to flood due to backflow

What does it look like from below? The best sealing on the outside is useless if the water then finds the next shortest way and penetrates through the floor. Even if you can get rid of it through the drainage around the house, the groundwater layer may still be pressing against it from below. I know this is not a solution approach. But since I have similar conditions, I just wanted to temper expectations for the newly applied insulation.