Well I'm glad that you didn't feel it a waste to reply 😉

Perhaps it was not your intention, but I must say that you comment seemed needlessly hostile. You could have instead writen something like 'You could be more efficient with your feedback by doing a and b, becasue x and z'. I'm just sharing my evaluation of your contribution with you and trying to provide useful feedback.

How is it a waste of time to read the comment another contributor has writen to you? I gave you the TLDR in the first paragraph. Even if it takes a few minutes to read a message which improves your future contributions; I'd say that's worth it. Do you not consider improving your skills progress? 

Perhaps I could consider cutting parts of the comment on a case by case basis, but I like to provide an explanation for why something should be done, not just state that it should. 

Sorry, but "This is not motivating at all." is not very constructive; I can't really apply that in future. Please elaborate. Why isn't it? How could it be made more so?

Regarding your mapping of buildings, I'll Echo my first comment, since I see you mapped them simillarly in a more recent [changeset](https://www.openstreetmap.org/changeset/172165368#map=19/-4.993917/21.407769). Generally the building footpritns are somewhat oversized, becasue they either include the shadow a building casts in the footprint, do not account for roof overhang, or extend beyond the roof/shadow visible in the imagery. 

Note the direction in which shadows are cast and use them to inform the size of features you map. Footprints of pitched roofs can be mapped smaller than the corners of the roof in imagery to account for overhang, so err' on the smaller side. I recommend viewing street level imagery to get a better undestanding of this; it can help a lot when mapping in dense areas. I think the follwing pages are quite useful https://wiki.openstreetmap.org/wiki/Key:roof:shape https://wiki.openstreetmap.org/wiki/Roof_modelling