Screed in the bathroom applied incorrectly - What to do?

Thanks first of all for the answers. The shower on the platform doesn't really bother me. Only before the purchase contract, we were told that only a barrier-free shower was possible. Because of the botched work, other options have suddenly become available after all.. And the promised and already paid special request service we will not receive anymore. We would like to have the money for the additional costs refunded. Only in the case of a shower on a platform this would not be possible, as the additional costs for it would be about the same..

Where is the problem? Remove the screed again. The installed screed cannot be the problem.

Apparently it is.. They probably want to avoid it somehow so that the schedule can be kept..

...whose problem and not yours...

Either manufacture a shower tray at no additional cost or fulfill the contractual performance.

I agree with Joedreck and would insist on contract fulfillment. Removing the screed is reasonable for the GU/BT. Alternatively, you can offer him that he may install a shower tray, but you will keep your 2,500 euros and he will also give you an extra week of vacation.

Apparently yes.. They probably want to avoid it somehow so that the schedule can be kept..

Chiseling out and manually applying new screed with a slope in the shower hardly takes any time. At least not enough to prevent the deadline from being met.
Is there underfloor heating installed there?