here's a technique breakdown. i mainly focused on the roof, but you could apply it to any area. the overall message is more clean and focused pixeling. Your drawing is great, but for it to be great pixel art, the pixels have to be very controlled. note the edit is still quite messy. it could be cleaned up further, but i think youll get the idea.
as for the outlines. generally hey are better used to add definition to an edge, but they can flatten the form pretty quickly, so if it isn't needed to see the edge, consider omitting it