To simplify installation, you can merge the base game, update, and DLC into a single NSP file using a PC tool called Swiss Army Knife (SAK) Requirements : SAK application, your console's , and the separate NSP files.
The game is a live service, frequently updated with new "Seasons" that introduce cars, tracks, and events. Major updates and paid DLC packs available via the eShop include: Asphalt 9: Legends | Nintendo Switch Game - Racing Game Asphalt 9 Legends Switch NSP -DLC Update- -eShop-