Congratulations on beating Dragon Quest XI: Echoes of an Elusive Age! While you may think your adventure is over, theres still a lot of things to do as the game even opens up more adventures just after the credits end. If you are up for another twenty to thirty hours of adventures, then get yourself ready to do more quests as thirteen more gets added in the Quest Catalogue.
Source: N4G PC Dragon Quest XI Guide – Quests List (Post-Game)