Walkthrough - Separation | Chapter 6 Metro 2033 Guide, walkthrough

Walkthrough: You'll exit the elevator in a well-known location and you should continue following your teammate #1. Don't forget that it can be risky here if you try moving too fast. Return to the metro car #2 where you'll listen to a new conversation.

I would strongly recommend that you use this opportunity to collect much needed supplies from a nearby crate #1, including a new gas mask, better guns, standard ammo and 30 rounds of gold ammunition. You'll also have to pick up a guidance system #2 and once it's in your possession you can enter the metro car to finish the mission.