TEW2 - am I just terrible or is this game hard as hell?

I'm not new to this kind of game but I'm barely through the first part and can't catch a break. I can only get maybe 4 bullets at a time and it takes all of those to kill one enemy. I read that you need to do more stealth attacks but I get within 10' of them and they turn around and book it straight for me, killing me in one strike. Am I completely missing something here?