On this task, the high-rise buildings are incorrect mapped.
You can see both one or more side walls and the roof. The Imagery is taken under a certain angle, so you can see more .
Often all visible walls and roofs are mapped as 1 building.
The correct way is to map the roofline and move the whole object on their footprint.
See this video.
https://youtu.be/dsfUcslLtVc?si=bEHwRl1sxDI_GA0H

Best regards and keep mapping