After the conversation with Sam head for the tunnel in front of you and keep going until you get to the exit.
Outside you'll find a campsite. Use it to get another entry from Lara's journal and upgrade your stuff before heading out. I don't recommend heading down the bridge. Instead towards the left of the bridge there's a wooden pillar make a zip lin from there to the tree on the opposite end and use it to cross the river.
Noe head up the path and you'll start hearing some voices. They're on the lower left area from where you are. Draw your bow and kill the one that's isolated from the other two.
After killing the first one go to the end of the path and aim you bow at the one wearing blue clothes shoot him then shoot the other one. It doesn't matter if you wait for them to finish their conversation they won't move anyways.
"After killing them jump on top of the torri and make your way to the other side. Drop salvage what you can then drop down on the lower ground and towards the platform where you killed the Solarii members.
Over at the other side of the platform you'll see a shrine. aim your bow at the beam and launch a rope arrow at it and use that to get down below. Enter the shrine and a cutscene will start.
After the cutscene jump across the gap and use the zip line to descend down the lower structure. Regain your balance after the fall and hide behind the wooden wall. Peek out and shoot the lantern to make the oil explode. then kill off any survivors from the explosion.
Don't head down the stairs instead go to the right of the oil tank that just exploded and keep following the path to the end. You should see a Torri. Draw your bow and kill the Solarii that's waiting below it.
Use the torri as a bridge and cross over to the other side. Then make your way to the top of the plane and shoot the Solarii underneath it.
Jump down and hide behind something. Then take out the Solarii that are hiding inside the plane.
Now head back down the path and towards the river.