You might 2-3 times while getting used to the mechanics, that’s just part of the learning curve.
Once you’re in actual missions you can lock doors so your marines can shelter and rest, this also counts as a save point that you can create at any time as long as you have tools.
So anything taller than your character breaks line of sight. Wait like ten seconds after it passes through the door then go the opposite platform from where you are hiding, keep behind the servers.
Get to a position that looks like the one you had been hiding behind at the start of that area right in front of the door.
Crouch down there until it is far enough way that you can get to the ramp without being spotted.
All you have to do is get to the hall in front of the exit in order to trigger the next cinematic.