Hello. Thanks for mapping on this project.
A remark about recognizing a building or a walled plot or courtyard.
You mapped a few courtyards/walled plots as a building.
Sometimes difficult to recognize.
When an object shows walls, with on both sides a shadow (on the inside of what might be a building)  It is mostly just a walled yard or plot.
Buildings don't show a shadow on the sunny side of a roof.
There is often a courtyard inside the building. You can then create a multipolygon to show the courtyard.
Best regards