1. Try to learn how to share images or image links.
Emmanuel have more important things to do than to fix all your post.
2.

probably the creation of the roof exceeds my skills !!

I don't think so. You've already do more things in your project.
Your roof is relatively OK but you have to make some small slop adjustments of different parts (wile you use also other roof parts than Generate roof).
Anyway you are on the right direction. Keep going!