GreedFall is a great RPG that should suffice for many hours of gameplay. The duration of the game, however, depends on your style of play and how much you decide to engage with the game world.
How long will it take to complete the main missions?
If you will only perform the main mission when playing GreedFall, you will find about 30 hours of gameplay. Part of this time you will spend talking to people and searching for materials.
The time may vary depending on your style. If you try to settle things by conversation, you'll avoid a few fights that would prolong the play time.
How much time can I spend on side quests?
If, in addition to the main plot, you want to focus on side quests and romance, you will spend from 35 to 40 hours in the game. It all depends on how smoothly the exploration of the world, and the battles go.
How long does the whole game take to complete?
If GreedFall will will really suck you in, you're looking at about 50 hours of exploring every nook and cranny of the game world. In addition, you can not only carry out missions commissioned by NPCs, but also use the notice boards, complete arenas, and for Serafeddin notes.