Subsequent sealing of the cladding and windows to the basement

Hello dear members,
it all started with the plan to renew the windows.
In advance, the building services and interior construction were brought up to date. The windows were not initially planned... But it did come to that after all. The windows will be replaced starting tomorrow.
A brief note about the house:
-Built in 1990
-Double-shell masonry with mineral wool
-Fully basemented (waterproof concrete)

A few days ago I removed the terrace on the west side so that the floor-to-ceiling windows can be properly sealed at the bottom. There are 7 windows along the entire length here.

At that time, concrete was poured along the entire length of the house in the terrace area. Directly against the facing bricks - without separation. Maybe too much was ordered back then - I can’t reasonably explain it any other way.
Initially, it was planned to entrust the waterproofing work to professionals.
When he verbally mentioned a rough (high four-digit) amount, I could hardly believe it at first. But I think the waterproofing is charged per linear meter. We are talking about approximately 250€/lfm. Perhaps justified, but unfortunately not an option for us.
I am a craftsman myself and familiar with waterproofing - though not for buildings.
So my ambitious plan is to tackle it myself.
Unfortunately, the waterproofing cannot be done according to current regulations; I have researched this somewhat.

I will upload some pictures as attachments for better overview.
I will try to create a sketch in another post.
I would appreciate some professional support.
Thank you to all readers.

Attached is a small sketch of the existing structure.

There was previously no sealing at the windows. The terrace surface was previously paved on sand. The sand in the area of the windows was mixed with cement to presumably gain some stability. Over the years, this has led to the screed in the outer uncovered area becoming slightly damp as well as some spots on the walls inside showing slight efflorescence. With continuous heavy rain, unfortunately, water also enters the basement, which flows slightly in the heavily watered area between the basement ceiling and the WU wall.

Basically, I have the following plan in mind:

- Remove concrete at the house and excavate down to the WU concrete.
- Thoroughly clean the entire surface.
- Apply primer and then level with bonding plaster.
- (Apply sealing slurry)
- Apply liquid plastic (with fleece reinforcement in critical areas).

The sealing is planned from the brickwork up to the WU concrete. The windows should be integrated when applying the liquid plastic.

Unfortunately, I do not really know what the guideline looked like at the time. However, I would pull the sealing from the WU concrete up to the Z-foil at the brickwork. Possibly remove some joint there to ensure a clean connection.

I look forward to any suggestions, improvements, or other advice.

Thank you very much in advance for the support.