How do I get past the second gate?
Solution 1:
As soon as you come to the first gate that the female orc is holding open, this ought to trigger a cut-scene. During the cut-scene, all the characters move through the first and second gate and into the large room.
If something else is happening here, such as a NPC disappearing and your characters not being able to continue, this is probably buggy behavior. (I have tried twice, and have not been able to reproduce this in my version of the game.)
It was difficult to determine specifically what version of the game I have. There are no version numbers anywhere that I could find. I am using the PC version released sometime during 2013.