Water leakage in new off the plan unit

Hi all, writing in to seek some advice and expertise on this. Happy to hear any. Also, sorry in advance for sounding like a mess because that’s exactly how we feel now.

Came in a week ago to our brand new off the plan apartment after getting keys and one day later as we are spotting the defects, we found water leakage onto our master bedroom wardrobe and entry to bathroom as the carpets were soaked. (Indicated on floor plan attached).

Took them 4 days to send a plumber over and finally found the source by cutting out a piece of tile in the shower area, water from unit above had been flowing out of an uncapped pipe within that cavity and likely through back of walls and/or floors onto our dry areas.

What should the solution be? My partner’s brother being an architect is concerned about spot fixing of tile affecting waterproofing. And I’m concerned about water soaking for too long traveling up the walls - causing long term mould problem etc. (you can see it’s been soaked for awhile thanks to rusty carpet nails).

We will definitely request for carpets to be changed and wardrobes which has been sitting on water to be changed etc. but anything else to take note of?