Hi,  thanks for mapping and welcome to HOT.

The buildings you mapped are well done as to their location. But pay attention to the squareness of the corners. Always draw buildings as square and precise as you can. Then add the Building feature type. And last, right click it and click the square icon. 

Please be more careful with tracing the outlines of the buildings. Zoom in as close as possible to see the outline of the buildings, hit each corner of the building carefully. Look for shadows, open ground, changes in roof color and vegetation to differentiate buildings. Your editors' Background settings provides the opportunity to change the Brightness, Contrast etc of the imagery. This can help to see buildings etc. more clearly.

Check out this article with basic information on how to map buildings: https://learnosm.org/en/hot-tips/tracing-rectangular-buildings/

Please watch these 2 short video for more info: 
-Buildings--> https://www.youtube.com/watch?v=Xs5wX592E1o
-Roads--> https://www.youtube.com/watch?v=ZBLwb2nisJQ 

Thanks so much for your contribution, Martien, HOT validator.