Sons Of The Forest

Sons Of The Forest is an open-world survival horror from Endnight Games, the makers of The Forest (published by Newnight). You are sent to a remote island to find a missing billionaire and soon find yourself in a hellscape crawling with cannibals and mutants.

Everything here rests on your own initiative: nobody hands you quests or tells you where to go. You chop trees, craft and build — from a small cabin to a whole seaside compound — gather food and defend yourself with pistols, axes, stun batons and other weapons. The seasons change: in summer you can catch salmon in the streams, while in winter food gets scarce. Mutants are everywhere, and some of them look almost human. You can survive alone or with friends in online co-op.

According to HowLongToBeat, the story takes about 19 hours and a 100% run about 55, so in a month at roughly 60 hours you can finish everything, though without much room to spare. There is a single-player mode that needs no friends, and co-op runs over the internet.