Hello. Thanks for mapping.
I noticed that you map buildings in a very weird way. Try to image that most buildings are rectangular and exists of lower buildings, often with rooftops and courtyards.  Often it is a building block. Difficult to recognize. Black lines are shadows. Large shadows from high buildings  

This message I send to mappers who are struggling with recognizing the building structure.

Check that walled courtyards or walled plots are not mapped as a building. 
Don't forget to square each rectangular building as well.

About mapping of high buildings.  They show a large shadow.
Difficult area to map.
Big building blocks with several stories and courtyards

Check here how high buildings ought to be mapped.

https://docs.google.com/document/d/1z7uDwYm4oNmlexHIhJxGCjPpNhCQAgRia5aEJr_4MwM/edit?usp=sharing

Many tall buildings have a small building, a superstructure, lift building or something similar on the roof. They give a shadow as well, so do not map them as a separate building, just map the roof lines of the complete building, and move the whole to the footprint. You can often see it in the shadow.

Best regards and keep mapping 
