Here's a few of the common issues people seem to have the most difficulty with when progressing the map (After reading the Main Page comments)

Train stop:
After jumping off the train and breaking through the boarded fence in the beginning, look at the bench to your left. It's underneath another bench that fell on top of it: You're supposed to climb up the benches, onto the ledge, and then make your way around to the billboard. From there, you're supposed to jump into the area that is being blocked by the locked fence (Crouch Jump).

Fight pit:
Explore the Fight Pit section and you should find a room that has injured refugees, a hole with an arrow pointing down in it, and 3 small gates on the wall that guard a Health and Armor station, and RPG ammo. Exactly opposite of that wall, there should be 3 boards with numbers under them. Press E on the first board, then jump down into the hole with the arrow. Do the same with the 2nd and 3rd boards when you complete the arena battle.

Combine soldiers:
When you're done exploring, you go to the door in the generator room that's guarded by rebels. When you press E on the door, a text pops up reading "This door should lead outside [End Game]." What you're supposed to do is that you have to press E on the door again (You might have to press it multiple times), and then you should be teleported into a room that's full of combine soldiers that are attacking rebels.