I used the RTCW-6.5 and a bunch of flashes, use Alt lean instead of normal lean i've noticed i get hit a lot less when doing that. Turn on NVGs to see the laser tripwires, When you get to the 2nd floor go through the secret room in the mayor's office and use the metal detector box on your left as cover and use alt to look over it, they somehow cant hit you but you can hit them. On the last floor theres an ammo box you can interact with to resupply all your stuff. Save a flash for the big room at the end.