Hi greens
Sounds like you have a fall and ponding issue. Chances are your building is a bit older? and built during older BCA standards.
Your problem may need the services of a professional such as a hydraulic engineer. They can analyse whether there is a storm water diversion issue and compare your problem to current standards.
You can find a good one here: https://www.masterplumbers.com/associations/ahsca/
A report usually goes for $800-$1200. Probably a good investment, especially if they find there is a definite deficiency in the building.