Puddle in front of shower tray - construction defect? DIN standards, building regulations?

Dear community, I bought an apartment in a developer project. A big plus of this apartment was a large shower. At the time of purchase, only the floor plan was available as orientation.



There is a
- shower tray 80x80 cm surrounded on 3 sides by walls with
- a tiled area of similar size in front of it, onto which one enters the "shower enclosure" through a
- side glass door.

THEORY: Following common sense, it was clear: "It must be tiled in such a way that water can drain within the enclosure."

REALITY: There is a step, so that water splashing out of the shower tray stays on the tiled area and has to be manually somehow pushed over the edge into the drain in the shower tray.

After multiple checks of the situation, the developer concluded that this does not constitute a defect because "splash water must be tolerated."

It must be built so that water can drain away, or not?! The developer has to provide a remedy, right?!

The only substantiated thing I could find on the internet was a reference to DIN 18195 Building Waterproofing Part 5. Quote "5.4 Through constructional measures, e.g. by arranging a slope, a permanently effective drainage of the water acting on the waterproofing must be ensured"
Unfortunately, I can neither verify this statement, as the document is not freely accessible, nor assess whether it even applies to our problem...

I ask for expert advice especially regarding the legal aspect.
Thanks in advance!
Regards, Sebastian

PS: Reducing the shower enclosure by repositioning the glass door is not an option for us, as showering comfortably is hardly possible on 80 x 80 cm.
Our idea was to enable drainage through an additional layer of tiles with a slope.

It would have made sense: a shower tray (80 x 160) cm or a continuously tiled shower.

Was there construction supervision? Is the area outside the shower tray professionally sealed? Can you find that out somehow? Ask the tiler?

Regarding the legal aspect: Since the developer denies a defect, you would have to sue. I would think about that ... Maybe it's better to have a large shower tray installed at your own expense. An end with horror instead of horror without end.

After multiple examinations of the facts, the builder concluded that this does not constitute a defect, because "splash water must be tolerated".
(...)
I am asking for expert advice, especially regarding the legal aspect.

Depends...

If the apartment has already been handed over and accepted:
Was the alleged defect (i) reported in the acceptance protocol and (ii) were warranty rights in this regard reserved despite acceptance of the work (§ 640 II Construction Code)?

If the answer to all is yes, the burden of proof for the defect lies with the builder; if not, it lies with you.

P.S.:
The sealing between the desired raised tiles in front of the cup and the cup itself also seems prone to damage to me... Not to mention the tripping step at the entrance of the door.

Is there some kind of pedestal constructed in front of the shower tray so that the shower tray appears recessed? I notice that the drawn shower door is dashed – dashed usually means optional equipment, but the question is how the builders envisioned this or what is standard (normal shower), how should the optional equipment be executed? Should this optional equipment door be a shower door at all or some kind of privacy screen, in addition to the normal shower door, which in any case should be installed on site?

: Don't you have a photo of it?