After you leave the Sewers you will start your second mission "Go past the Harbor".
The First Campfire
In the Campfires, the player is allowed to save the game.
Holding E to do a Quick Save or hitting Q to Save the game (with the option to select the save file).
The Tree and Items
In the first zone of the Harbor, you can find a lot of items scattered in the ground (for example, Arrows for the Crossbow Weapons).
Also, there is a tree in the top of the hill where is a zone to take a first peek of the full Harbor zone (useful to start making a possible route to evade enemies).
Hide in Grasses
In the game, there is a type of grasses where you can hide if you crouch in them.
When you are hiding in grasses, enemies can't see you (useful to evade enemies).
Throwing Rocks to Move Enemies
If an enemy blocks your pass, you can throw a rock to a zone and the enemy will follow the rock (useful to open zones where enemies block the path).