The guys on the ledge above will also throw dynamite and Molotovs. So you'll need to multi-task. When you see incoming explosives...
...quickly scramble from one safe spot to another. Then continue firing.
If Lara takes damage, release the Aim button briefly so she can crouch behind cover and heal. Remember she's vulnerable while she's shooting.
You may be able to survive by simply moving back and forth between the two sets of barrels near the entrance, but if you like, you can also run to the left side of the stairs and take cover there (as shown by the arrow on the right in the screenshot above).
Or duck behind one of the boxes sitting in the pool next to the stairs (as shown here and indicated by the arrow on the left in the previous screenshot).
Most of the men come around the front of the stairs to get at Lara.
Be sure to watch your back, though, because a few sneaky guys will move under the staircase and approach you from behind.