Keep moving forward with Jonah towards the objective marker. After a while you’ll come across Trinity patrol. Stealthily kill the first guard. Move forward while hidden and take the left path. Ledge-takedown the guard and climb up. Moving forward will start a cut-scene in which Lara and Jonah bet under the armoured vehicle. Crawl forward and takedown both the guards standing behind the vehicle. Remain hidden in the bushes until the guard turns around, and then take him out. Move forward and climb the ledge. A cut-scene will start. Enter the cave and move forward. You’ll hit a dead end and you’ll have to burn the barrier with fire-arrows to clear the path (“Oil” required for making fire-arrows is lying there). Exit the cave to reach Kuwaq Yaku.