Welcome to OSM. Generally you identified buildings here, but you mapped two pairs of buildings that share common nodes. Please consider the roof shape and shadows of buildings to determine where one building ends and another begins. If you cannot determine, then it's safer to assume they're seperate. 

Please do not connect the corners of buildings to other buildings or features such as highways or residential areas. In the iD Editor, hold down the `Alt` key to prevent your cursor from snapping to existing data and accidentally creating shared(grey) nodes. This [video about connected nodes](https://youtu.be/ltn1VOiq5_0) has more information and a guide.

Thank you for your contribution. If you want to experience the OSM community or to get timely feedback from other mappers; I recommend that you attend a mapathon. You can find events here https://osmcal.org/