The adventures offered by GreedFall will offer you dozens of hours of gameplay. However, if the content prepared by the developers isn't enough for you, you can check the mods. The creators of these modifications have prepared a variety of new features - improved the camera, changed some gameplay elements and influenced the mechanics of the game.
Currently (September 2019), Steam doesn't offer options for modifying GreedFall. This means that you cannot simply download a mod from the Steam Workshop.
NexusMods is a platform with the biggest number of modifications for GreedFall. There, you will find mods of all sorts, from those that only change the cosmetic aspects to those that affect the entire course of the game.
Each of the mods on this site has its own instructions. Just look at the bottom of the page to check what you need to do.