Firstly, peek (strafe) to the left a little. Equip Dragunov and look up. There's a guy patrolling. Snipe him. Go straight to the weapon storage (there's a picture next to the door). Go left to take all the weapon. You'll see a tunnel to the right. Go there and kill a man with Mp5 SD3. Take the AK47 and equip it. Follow the tunnel until you reach the next room. There are 2 enemies there. The first enemy is on the upper right corner of the room and the other one is on the bottom left corner of the room. Kill the first enemy first, then the second one. Use the elevator to go down. After you reach the second floor, exit the elevator to the next tunnel. Open the next door. If you are on time, you'll see a guy walking on the left hand side. Then, you'll see the next enemy on the right hand side.