You start off near a small passageway. Start moving forward. Open the nearby door carefully. Enter the new corridor. You should see a single terrorist on the other side of the glass (#1). Kill him and one of his colleagues, that should arrive there shortly. You may continue moving towards the opposite end of this corridor. Open a new door and enter the next room. Zoom in the view. Thanks to that, you should be able to take out new terrorists without any problems (#2).
Enter the next room. Start shooting at visible enemy soldiers (#1). Keep moving at all times. Don't stop, because that would have made you an easy target. I would also recommend using nearby pillars for extra cover. Furthermore, you mustn't forget about reloading your weapon frequently. Ignore the laptop located in the central part of the room. Head on towards the opposite exit. After a while, you should locate a ladder (#2). Use it in order to get to the lower level of the complex.
Don't wait for the rest of the team to get here. Stand by one of the barriers. A group of enemy soldiers will arrive here shortly (#1). If you're lucky, they won't even have an opportunity to turn around. Get down to one of the lower levels. Start shooting at those terrorists who will be guarding the main entrance (#2). You might also consider throwing a couple of grenades at them, however this is a risky manoeuvre.
Start moving towards the ground floor. Bear in mind that the entrance may still be guarded by a large group of enemy soldiers (#1). It would be best to send your team to handle this problem. After that, head on to the nearby corridor. Start moving forward. Lean out carefully. I would recommend throwing a couple of grenades at the guys standing in the elevator (#2). Alternatively, you could try and score a few heashots...
Enter the elevator. Sadly, you can't activate it. There's a ladder on your right. Use it to get to the top of the elevator (#1). Once you're there, head on to the second ladder (#2). This time you will have to go down. WAIT for the rest of the team to get there. It will probably take them some time (at least 30-40 seconds...).
You will find yourself in a large basement. Start off by killing all nearby hostiles (#1). You have to be very careful. Some of the terrorists will probably attack you from the left flank. Once they're gone, start moving forward. You will be encountering additional enemy units along the way (#2). Use barrels and pillars for much needed cover. I would also recommend letting your teammates take part in these fights.
There's only one more thing to do here. Step up to the designated area (#1). Wait for the rest of the team to show up. The game should load the new map in just a few seconds.