Finished district 3, the district where you live. You can upgrade your house once, to add a second floor, and you’ll always be able to change wallpaper and flooring.
So, that means district 1, 3 and 4 are finished, as well as the forest. Only district 2 and the beach are the only main maps left! District 2 will be easy since it’s just the town’s square with a town hall (excluding the festivals that are held there, I’ll worry about that later).