Civil / Structural Engineer for concrete slab waterproofing

I am in the process of pouring the concrete slab for the rooftop of my building. that rooftop will be used as a restaurant, which mean HEAVY FOOT TRAFFIC.
I am looking for a Civil / Structural Engineer with the most appropriate experience with this kind of jobs, that will advice on the most optimal different ways to seal the concrete slabs surface for ABSOLUTE leakage-free inside of the building.

*****I am putting a video that is showing the exact type of pouring we have doing on the building. PLEASE WATCH TO HAVE AN EXACT IDEA*****

https://www.youtube.com/watch?v=fVs26ViaOiw