Nice work. The normals (that is, the direction of the polygon faces) on the house need to be fixed. Whenever you see a part of a mesh looking dark like that, it’s because its facing the wrong way. Select the house, press Tab to go into edit mode press A to select all then on the menu to the left under where it says “Extended”, click the small triangle button (it’s a picture of mesh lines, it is the mesh cleanup menu) which is next to the vertex, edge, and faces menus. Then press “Fix Normals” which will make sure all the mesh faces are facing the same direction. You can also adjust individual faces by pressing “Flip” to flip the normals instead.