This adventure is rather poorly designed. It's simply five trolls in a line, that come out and make a demand one after the other.

A far better design would be if the trolls used their treasure, or stored it someplace interesting, and the PC's had some way of knowing what hazards were before them. A sign or intelligent troll at the start, to tell them the deal. As it is, this is just a bridge with trolls on it -- literally something a GM could do on their own out of the monster manual.