Go down the escalator and a groupof thugs will come after you. Unfortunately the one with the gun won't be the one to approach you. So go ahead and surprise kill the machete guy and shoot the one holding a gun, then take care of the rest.
Climb down the escalator and head straight towards the fire. A cutscene will play, point your gun at the guy with the machete after the cutscene.
From the campfire turn left and head for the mesh gate. Approach it then press E and spam the LMB to get it open. Once it's open head inside.
Head down the stairs and into the subway. You'll find some survivors camped here, you can take some of their supplies. For those who are playing on Steam, don't eat the meat from the pot. It's human meat and there's an achievement for not eating it.
Climb back down the tracks and head to the right side. Keep going until you reach the end of the tunnel and crouch down to pass through the rubble.
Go down the side of the track and make your way down using the small stones around the area until you get to the pipe. Then use that to keep climbing down towards the fallen train cart.
Climb back up on the rocks and make your way past the pipe you used to get down and towards the right. There's a small platform there that you can use to rest.
Start climbing the rocks again and continue to make your way to the right. You'll find a stone that's really far from you. Hold space and D to jump towards it then continue to move down. When you can't move down anymore press the RMB to drop down.
Get around the path and you'll find some parts of the tracks that fell. Climb up on the metal studs and get to the top of it. Once there jump a large jump to the right and continue up.
Once you get on the surface, turn left and you'll find some metal bars that you can use to climb up higher.
Get near the side of the stone and continue working your way up, then to the left until you get on the hanging train. You may wanna use a piton or a drink here.
Walk down the inclined sloped part of the train and hang on the edge of it, then make your way down through the metal ledges and pipes.
When you get to the very bottom, drop down right in front of the edge of the next car. Pull yourself up and exit back into the subway.
Head down the tracks and pick up the shiny thing on the right side, above the stairs. Those are bullets and you're gonna need them in a bit.
Go further into the tunnel until you start seeing some dead bodies on the floor. Take out your gun and walk a little bit more. Those three guys will ambush you, shoot the one with a gun.
Point your gun at the other two and make your way around them to pick up the bullets from the one you just killed. Now shoot the older one and aim at the last one. He'll surrender when he's left alone.
There's a hole on the left side of the tracks, head for it and drop down on the side. Make your way around the metal edges until you can drop down on the tracks below.
There are more thugs down here. Wait for the armed one to start pushing you around, then kill him. Quickly shoot the other one with a gun afterwards.
There are three left now. Shoot the larger guy and point your gun at the smaller two. They should surrender after the big guy is gone.
Proceed down the tracks until you reach the end. When you do, turn right and enter the sewes. To the right again, there's a path so head down there and up the stairs inside.
You'll exit out into a parking lot at the top. Turn right and keep going until you see a fork in the road, when you do turn left and you'll find the elevator. Head inside it.