Remove the outside edge loop for starters. The corner poly is a triangle, follow what I mentioned first, that should turn that into a quad, then post an update.
I'm bored writing Python so here it is. From right to left. - Start with blocking out the slope and general shape of the door. - Select the top edge of the door and extrude down. Use scale tool and squeeze it in Y direction so it's flat. Use "v" key and snap it to the same level as the bottom vertices. Merge the vertices…