Hi,
Welcome to OSM!
Thanks for the initial contribution. Looks like Maxar imagery is more upto date than Bing in this area. 
You certainly have taken the bull by the horns! A few hints? Keep it simple, Do small bits at a time - map the building by itself ... then separately map a footpath.. this makes it easier to follow what the warning are talking about as you will have less of them to understand. 