THE 3 GUYS ON THE RIGHT SIDE OF THE BRIDGE
The guards near the bridge entrance are both dead, which means you can now safely open the main gate. Once you?re on the bridge, check the position of the 4 guys patrolling the left side of the bridge. The lights enlightening the bridge can easily reveal your position, so just wait till these 4 guys are going away from you (or are too far to spot you), then jump off the right side of the bridge and swim on the shore. Now you?re going to kill the 3 guys located by the nearby shack. As you can see, 2 of them (one armed with AK47, the other with MAC10) stand still, staring at each other, whereas the 3rd guy patrols the area behind the shack. You?re going to kill those 2 standing guys first. Once again, there are various ways to kill them, but I would recommend mainly 2 approaches:
1st APPROACH: See those nearby crates? Carefully CRAWL to the right side of them to be as close to the AK47 guy as you can whilst his buddy won?t be having a look at you (see this pic). One quick headshot from your silencer ? and the AK47 guy is gone! The other guy will of course notice the killing, but he will only run away a couple of meters and then return back to his original position, staring directly at the corpse of his buddy as if nothing had happened (how clever!)? Now you can easily approach him from the back and twist his neck. Alternatively, you can even use the MP5A3 submachine gun to kill the AK47 guy (in order to save some ammo for your silenced pistol).
Anyway, if you don?t want to waste any time killing the 2nd guy, you can also try an alternative, a bit quicker approach. As you may noticed, once you kill the AK47 guy, the MAC-10 guy will always run away and stop at the one and the same place near the crates, crouching there for a while. Therefore, you can try the following: once the AK47 guy is dead, go ASAP around the crates (using the CROUCH-WALK mode together with strafe keys, of course), and then kill the MAC-10 guy from the back (see this pic). He will always be looking to the direction just enough for you to not be spotted (I?ve killed him literally million times using this alternative approach, but he didn?t spot me even once!), so if you didn?t waste any time, you should have no problems to kill him.
It?s worth of mentioning that this whole 1st approach has one, if minor drawback: once the MAC-10 guy notices his buddy dying, sometimes his scream will also alert the guy patrolling the area behind the shack (who?ll start running back and forth), so you?ll have to wait some time till he ?calms down?.
2nd APPROACH: It?s my favourite one, because it ensures you will kill both guys by twisting their necks ? and they won?t even notice each other?s death! It?s almost similar to that ?alternative? version of the 1st approach (i.e. you?ll kill the MAC-10 guy from behind by going around the crates), but this time, you won?t fire a single shot? Once again, it?s very easy, reliable and quick tactic! First, position yourself as close behind the right side of these crates as you can in order to not be seen by any of the guys (see this pic). Now start doing quick noisy steps in RUN mode (forwards and backwards, of course) till the guys scream out that characteristic shout of being alerted (by doing this, you?ll ensure that both guys will be looking at the same, opposite direction, when approaching them from the other side of the crates). Once the guys are alerted, immediately kill the MAC-10 guy by going around the crates and then twisting his neck, and once he's dead, hug ASAP this nearby corner between the crates. If you did it as described, the other guy will maybe hear his buddy?s corpse falling on the ground, but since you and the corpse will be well hidden behind the crates, he will only utter something and then return to his original guarding position as if nothing had happened. You can then easily kill him from behind, but be quick, because once he?s back at his original guarding position, it usually takes him only a couple of seconds to finally notice his buddy?s corpse. Therefore, I would usually kill him already when he?s returning to his original position. Just use the peaking to know when he starts walking back, and then approach him diagonally in CROUCH-WALK mode (using strafe key, of course), but don?t move too soon or he may spot you!
The remaining guy is very easy to kill. As you can see, he?s patrolling a relatively dark area between that large container and the fence. He always stops at each end of the container for at least 5 or so seconds, giving you all the time in the world to hide behind one of its corners, and then approach him in CROUCH-WALK mode either when he stops near it, or when he?s walking towards the other side of the container (see this pic).
CLEARING THE BARRACKS
Now the 3 guys located on the right side of the bridge are dead, so grab all the grenades from the nearby shack (the dead AK47 guy can occasionally give you one as well), and then RUN around the whole complex till you reach the main entrance. Open/shoot the gates and return back to the area near the barracks.
Now you have 2 options (it depends on your choice):
1. If you want to just kill the 4 guys inside - without wanting to collect the AK47s and also grenades which they occasionally leave, forget about it now, and just continue with the mission as written below.
2. If you do want to collect those AK47s/grenades, you may try the following:
Slowly approach the barracks' entrance in WALK mode, and stop just before that stony door-step (if you step on it, the guys inside will hear you). Unfortunately, the doors leading inside always shut, and you can?t open them either (unless you?re inside), so the trick is to lure the guys out with a couple of quick shots to their legs and then kill them with a grenade as they come out. Of course, you can just fire a couple of blind shots (or make a couple of noisy steps), and they?ll come out, but why not to do some damage if you can? Of course, you can?t see through the doors (which makes a good aiming that more difficult), but don?t worry. Just activate the thermal vision. As you can see, the 2 guys on the left stand in the same line, which means you can hurt them both (if aiming properly). The trick is to point the aim directly at their feet (if you point at their torso, chances are you may kill one of them, in which case the corpse + the weapon will remain inside).
Since you can?t see any crosshair when using thermal vision, accurate aiming may seem impossible at first, but don?t worry ? it is possible! How come? It?s easy! Just notice those mesh-like things when looking through the thermal vision. As you can see, they?re nicely aligned and form narrow, parallel lines in both horizontal and vertical direction. Since your view is only limited to a certain kind of ellipse (which is nicely centered), you can easily distinguish the center lines in both horizontal and vertical direction, and thus find the mesh which is located in the absolute center of your view (see this pic). So all you have to do is to point that center mesh at their feet, and you?re guaranteed of perfect aiming (provided you don?t move with your mouse afterwards, of course).
Now switch back to normal view and RUN mode. Fire a couple of shots with your MP5A3 submachine gun and immediately run backwards until you?re in a safe distance (roughly 40-50 m away). Equip the grenades, and wait in CROUCH-WALK mode till all the guys come out (in crouch-walk mode, you?ll be least visible whilst having an opportunity to throw grenades). Now try to kill them with one good grenade throw when they?re close to each other. It?s tough to kill them all with just one grenade, because they?re usually running to all directions, but it?s possible. Anyway, if someone of them remains alive, just finish him with your silencer (shoot to the torso and lie in CRAWL mode, of course). Obviously, the best opportunity for you to shoot them is when they're running straight towards you, since then they're moving sideways only slightly. Just don?t throw any grenade when some of the guys are still inside, or you may never collect their AK47s/grenades.
2 REMAINING GUARDS NEAR THE TRUCK
Now get as close as you can to have a clear look on both guys + the nearby camera (of course, be in CROUCH-WALK mode), whilst being in a safe distance (roughly 40 m, somewhere near those crates on the right). Your goal is to throw a grenade in a way that it destroys the camera + kills at least one (or both) of the guys. It?s not an easy task, because one of the guys (if not both) will always run away, so usually you?ll kill only one of them. Anyway, your top priority is to destroy the camera, since it can raise the alarm when it notices the corpse on the ground. Usually, when you throw the grenade, the guys will run somewhere near the truck, so you may wait till the camera starts turning to the opposite direction (i.e. to the north), and then try to throw the grenade as close between the 2 guys as possible. Of course, it takes some time till the grenade detonates, so use this brief moment to quickly destroy the camera with your silencer ? and that?s it! It?s just a matter of 2-3 tries till you learn how to deal with this situation?