After one of the shortest chapters, you get one of the longest. There are distinct breaks between mini-scenarios on your way through Lazarevic's stronghold, and they help with the pacing, but it's still a very long chapter. The goal is to make your way through tons of Lazarevic's outposts to the main part of the Monastery, still attempting to rescue Schäfer from his no doubt awful fate. The action happens in stages with a bit of slowdown in between, usually having to do with platforming. When the action starts back up, you'll be able to start out stealthily, so use that to your advantage.
A silent beginning
Start out by climbing the rest of the way up the cliff, then take the path around to some more handholds below a guard. When his boss walks away, stealth grab him while hanging below after his boss gets a little ways away. Jump up and get cover behind the crates at the back of the truck and watch the commander's conversation with the other guard. The guard walks back toward you and posts with his back to you, where you can stealth attack him. Head around to the right of the truck you're behind and head up the side of the truck when you see the guard at the end of the area turn back around after talking with the boss. Get cover to the side of the crates by the guard, then wait until the boss continues his patrol past you to take this guard out as well. Quickly follow the boss around the truck and stealth him, then go to the front of the area and take out the last guard in the same way. Go up the stairs and follow the path around the mountain ahead of him.
At the top, take cover behind a large step and check out the guards beyond. You can cross the last plank in the bridge ahead, then get cover behind the low wall there and wait for the guard on the right to lean against the corner of the building. Sneak up beside him and stealth him from around the corner, but take your time, because if one of the underling guards inside sees you while he's walking to where he sits down, he'll alert the guards. You can stealth all the lower guards, meaning all the ones that don't wear black outfits. If you take out the higher ranked ones, the guards will start to notice. If you have extremely good timing, you can make a cover-to-cover move to the low wall right beside you and wait for all the guys inside to have their backs to you, then hop the wall and take out the guy going back and forth to the fire barrel on the outside landing. From there you can stealth grab the guard sitting on the wall with his back to you. Watch the two guys in black patrolling inside, then when their backs are to you, go back to the edge of the platform over the chasm and jump to the climbable stones on the building beside you. Take these over around the side until you can jump to the next wooden platform where another guard is patrolling. Stealth him when he walks over by you, and that marks the last of the regular soldiers you'll be able to take out.
Take out the machine gun
Move into the dark building from the platform, and you'll find some more weapons and a grenade. This is a good place to start your assault, because it provides good cover and you'll be able to see across the courtyard to where the enemies start dropping in. Elena will join you, and you'll know you've got them all when she takes off to the middle of the courtyard, and finds cover behind some low walls by the bridge. There's a machine gun emplacement on the other side of the river, and you'll need to push the cart in the middle across to get to the other side. Crouch behind it and push it like normal. When it gets over there and stalls, a bunch of guys will assault from the front and right. Drop down to the lower platform on the left, then quickly take the log across below the bridge. Jump to the climbable stones you'll find over there, then go to the top of the ledge and stealth grab the two guys at the top and shoot two more guys on the stairs. Hop up and grab some cover, then work on taking out the remaining three enemies up here, including one of the heavily armored shotgunners.
Jump down toward the machine gun, making sure to stay behind the walls to the right. This leads you inside the building, where you can get around behind the machine gun. The gunner isn't alone, so use a grenade to clear them out, or grab the propane tank from when you first started entering the building and use that. Wipe up the rest of the guys and get behind the turret, because Elena is getting assaulted and you need to protect her while she gets over to you. Guys drop down all over the place on the other side of the river, so just light them up, making sure to take out the guys closest to Elena first, then the ones with laser scopes. When they're all dead, Elena will tell you so, and you can go back into the building. At the other end is a doorway you can open by cranking the chain mechanism on the left. Make sure you tap 
the whole time, or you'll drop the door.
Get into the tower
The pathway is broken beyond the door, so you'll need to get the rope below you for Elena. Climb the red boards on the left down, jump to the inside wall and keep going down to the bottom. There you'll be able to jump across to the ledge with the rope. When Elena gets down, cross the fallen beam to the other side. Once there, jump across the gap to some orange stones and climb them up and around until you can jump behind you to another ledge. Turn around at the ledge and face Elena, then press to have her jump up to you. Go around to the other side of the statue and crouch behind it. When Elena joins you, push it over to create a way out. Climb up the statue then head out and around to your left, edging around the stone along the narrow boards. Climb up the rope at the end to catch a glimpse of Lazarevic with Schäfer. Follow Elena up some steps on the other side, then jump to more steps you can go up. After another jump and some more steps, you'll find yourself at the top with a locked door.
Head behind you to the other side of the platform across from the door, and go left around a pillar to the very end where there's an open archway and another white pillar. On the other side are some red boards you can climb up to the top of the structure. There's a platform on the top, from which you can jump to a beam sticking out on the other side of the main area where Elena is below you. Jump over to it, then take it around until you can jump to the bricks in the white wall of the building you're trying to get into. Jump over to them and take them around to the other side of the building, then up and back around the same corner. They eventually lead to the wooden platform above the locked door. Climb up onto it and take the red boards farther up the wall until you can jump to a red post. Take those to the right and swing across them all the way around to the other side where you can make it to another platform at the top of the building. Stealth grab the guard, and climb up.
From one building to the next
On top of the roof you'll see a short beam sticking out from one side of the floor and a guard patrolling on a landing below and to the right of it. When he's facing away from you, walk out to the end of the beam and jump to the smaller wooden beam spanning the gap above him. Drop down behind him and stealth attack him. There is a guard patrolling on the other side of the room, and he spends most of his time looking the other way. Wait until the sentry across from you is at one of his stopping points, then cross the beam to him and take him down. That's the end of the stealth portion, because as soon as you get set foot on the next floor down, all the guys will somehow be alerted to your presence. Use cover and move around as needed while you clear the floors from above. There are four guys on the floor below you, and groups on each of the floors below that. When you've cleared them all out, head to the bottom to open the door for Elena.
When you do, the wall will be blasted open and you'll find yourself under attack by an RPG gunner in the next building covering the guys coming across the bridge. Get to cover behind some crates in the middle of the room with a Dragon Sniper behind it. Use that to take out the RPG gunner first, then the approaching bad guys. When you run out of ammo, switch to something else and continue taking them down. They have to come to you from one narrow approach, so take your time and pick them all off. When that's over, head over to the next building. There are a bunch of tough enemies in the next tower, so you might want to pick up the riot shield or a SAS - 12 shotgun before you head over, to help you take these guys out. After you've cleared the bottom floor and the guy shooting you from above, go out the hole in the wall in the corner just to the right of where you entered. Climb down the white stones there and around the building down to the Carved Wooden Ghurra.
Take out the sniper nests
Head back up and boost Elena up the ladder at the back of the room. When you follow her up, some guys come down to the floor above and you'll still have to watch for the snipers with their laser scopes coming through the broken walls. You may not be able to take out all three of the guys that come from above from behind the crates at the top of the ladder, so cross to the other side of the room, away from the snipers, and take them out from there. Climb up two more ladders and go around the floor to an opening in the wall. On the outside of it, you'll be able to climb some red and white stones to the top of the building where you'll find some sniper rifles. Across the way, where the snipers are firing from, you'll see four large towers. The first thing you'll want to do is take out the RPG gunner on the lower balcony of the second tower from the right. After that, start picking off snipers. After killing one, move to another cover location or they'll hone in on you and take you out when you pop up. At the same time, a bunch of bad guys will cross the bridge to you. Take out all the snipers (don't forget the one down at the end of the bridge) and the other enemies.
Now that no one's shooting at you, go back down to the very bottom of the building and out the side in the direction of the sniper towers to where a broken bridge used to be. It leads to a ledge across a large gap. This is a tough jump to make, but it's doable. On the far side, take the two ladders down, then shoot down the treasure on the wall at the bottom to get the Bronze Tiger Bell. Head all the way back up to where Elena is waiting for you. Cross the beam to the real bridge where you'll spot Lazarevic and Schäfer again. Start running across the bridge after Elena, where it breaks apart and falls. You'll need to climb up the bridge when it crashes, so just keep heading up, jumping across where you need to until you reach the top. Once you're up there, open the door with Elena and head to the top of the stairs for a huge fight in the main courtyard.