Where the hand of Daishi? (Far Cry: Primal)

way more like what ito trees is closed no?( Like the entrance to the cave) I Remember like down the passage of the plot you will see this cave .

and these trees, even the fire are not burned, then will come the quest will be in this cave

You need to go all the way in the quest. Near a small cave, after you pass the timber will rise with a hook upstairs. Well, there will understand. Good luck.