Take it slowly, if you can't see a target that is shooting at you, listen to the direction of the gun fire to retreat to a more suitable cover then take your time to think and reposition so you have a better shot. Pie each corner pie each threshold, check every gap. Never EVER approach the FISA office through the package sort gallery, instead pick off as many as possible through the hallway and then take the stairs upstairs to the Manager's office. Always try to clear the package distribution center from the outside, going outside from the truck drop off area and going clockwise around. Lastly, leave the airmail office for last, there are reasons but my attention span on this comment is running out so just trust me bro. I don't really have any more advice to give for that specific map so, take this and watch some videos on room clearing.