Complex sentence: Eventually they get to work under the supervision of Trygaeus and Hermes, pulling boulders from the cave's mouth, but some of the Greeks are more of a hindrance than a help and real progress is only made by the farmers.
Split into simpler sentences: Eventually they get to work, pulling boulders from the cave's mouth under supervision by Trygaeus and Hermes. Some of the Greeks are more of a hindrance than a help and real progress is only made by the farmers.