When you first arrive in the jungle region of Vanaheim in God of War Ragnarok, you will find there are some aggressive trolls at the other side of the island that are throwing large rocks at you. Throwing your axe at them may inflict some damage but those little elf creatures are chanting nearby which results in them healing instantly. The only way to kill them is to get to the other side but how do you get there?
This is going to be one that you do not get to solve for a while. You will need to ignore them for now as the way across is not available. If you take the other path and go ahead in the direction it leads, you will find yourself at a large dam that looks down on the jungle region of Vanaheim. There will be a quest objective at this point asking you to lift the gates on the dam to let the water come back down.
Once you have cleared the brambles blocking the dam gates, you will find that water has been restored to the jungle region below. When you climb back down, you will be able to get into a boat and this is going to be the key you need to get over to the trolls throwing the large rocks.
To find the dock, you will need to take a boat back toward the opening that you used to get into this jungle area in the first place. The little gap between that platform you were standing on and where the trolls are is what you need to travel through.
Once you get down the river and to the other side, you will spot a dock that you can use to get out of the boat. Go through the crack in the rocks and you will be able to take out those pixi, elf things that are healing the trolls before taking them on and killing them.