Follow Nadine and when you are on your way you should use your grapple hook on one of the hooks. Soon, you will get closer to two guards. This is a perfect moment for using a team attack - Nadine can attack the guard on the left and you can eliminate the one on the right.
Move forward and start climbing the tall wall. When you reach the top you must jump from the wall and you will start sliding on a slippery ground. During this part you must shoot the first enemy that will appear in front of you.
Another enemies are occupying nearby ruins but engaging them in combat isn't a good idea because an armored vehicle will soon appear in the ruins. You don't have any grenades nor rocket launchers so start running through the ruins and during your escape you should use covers and kill only those enemies that are on your way. You also need to climb in a few places and when you do that you should try to be exposed as rare as possible.
During your escape you should be careful, e.g. in the place from the picture above where you have to catch a hook while you are sliding down. The path that leads through the ruins is rather linear but even if you get lost you should find Nadine and learn where you need to go. Your goal is to reach a small closed gate which you and Nadine have to open.
You are now in catacombs and, luckily for you, you don't have to be afraid of armored vehicles and enemy mercenaries. Look around the starting place because a treasure (6/6 - Khanjarli Curved Dagger) can be found near one of the skeletons presented in the picture.
Find a small hole near the ceiling and use it to leave this place. In the next location, examine the smaller wall with an aqueduct behind it and then, climb up the bigger wall that sun shines through. This will play a new cut-scene.