Hello and welcome to OSM!

I'll explain some tags to you:
building:flats is for the number of units in a building. This is an apartment building, so building:flats means the number of apartments in the building. Not very useful. You marked it as 20,000, but the building doesn't have 20,000 apartments. I guess you wanted to add the postcode. That goes into addr:postcode.

building:levels is the number of levels of the building, including the ground floor, meaning this building has 6 levels.

addr:city is, well, the city. But there's really no need to add it because there's already a city boundary for Casablanca, and everything that's inside it already has Casablanca as the address.

There's no need to add a point for "apartment complex". You already added all the info to the building.

You can also notice the building is badly mapped. That's the case in most of Morocco, but you can nicely draw them yourself by mapping an area, selecting it and clicking Q to square it, and marking it as an apartment building. You can check out quartier Racine where I drew all the buildings.

Thanks and welcome again!