Is to learn voice commands. „Hold your fire“ and „knives only“ can save your live multiple times. If a PMC responses, pull out your knife and hit the wall to show you put your gun away.
This is exactly how tons if not hundreds of lower level players have survived an encounter with me in my 6000h game time. I like to help them out because we were all once at that stage. I usually drop them loot and escort them to the extract as well. There are a lot of people like me out there that would do the same. Even if you are a BEAR the experienced players know the voice lines and know what they mean. Especially on labs people team up for fun no matter if it’s a bear or usec because they know how the Russian voice line sounds like.
Next time you are desperate trying to finish an objective, use those voice lines if you encounter a pmc. If they don’t respond you can still chad it up and risk it. But if they respond this might change the outcome of your raid entirely.