Hello. Thanks for mapping here
An urgent recommendation: 
Please map each building accurate and square it (rectangular) with the Q key in the editor. Keep the building selected during pressing the Q key
Most buildings are good rectangular and the mappings should reflect that.
A hand drawn building is mostly not correct rectangular. Therefore use the Q key after mark it a building and the object is still selected. 
Be aware that this will not work when the deviation to a square corner is to big. Then you have to adjust the building manually . After that you can square it again.

Please take your time to map accurate. You will waste Validators time if they have to correct lots of inaccurate mappings.
Use a mouse to draw.

Never let a node of a building connect to other features, like highways, other buildings  or residential areas.
To avoid that , In iDeditor keep the Alt key down while drawing the building. In JOSM keep the Ctrl key down

Map each building individually. do not cluster buildings and call it 1 building

Please pay also attention on the issue triangle on the right-hand menu 
It alerts you on warnings and errors.

Please (try to)solve these before uploading your work.

Best regards and keep mapping !