Fuck mate, me too, I'm on this level and wtf, it's so hard

Constantly face them and slowly back away if one of them sees you. If they start rushing you, either run away or unload all your ammo into its face.
Metro 2033 is one of my favorite games :D

I'm stuck on this level, the only weapon I have that kills them quickly is the magnum with a suppresor and a scope, the others run out of ammos before killing even one

You don't have to kill any of them though, just face them and slowly back away and they won't attack you.

What ? They just attack me when they see me tho

DONT KILL THEM. Make sure your cursor is pointed to their face and they'll leav you alone. Back away very slowly. :)

I didn't sign up for this. I didn't sign up to stare a ugly tumor gorilla in the face. Motherfucker sprints as soon as he's obscured by cover.

Sneak and hide.
Don't move slowly or quickly.
Move smoothly, because smooth is fast.
This is the part of the game where you're playing Splinter-Cell.
Remember that, and things will get easier.
.
Assuming you're still there, that is...

Ok so I tried this morning, and when I get to the part where there is two of them in some sort of cage and one goes though the ceiling, the one that stayed just fucking attack me even with the stuff you said

If all else fails just run like hell.

Dude i'm sorry you must not be so good at the game... like I struggled coz i didnt know what to do. Googled I had to look at it's eyes and got away first try

If one of those things start hooting at me I'm just going to book it and toss dynamite everywhere.