Complex sentence: Charlie lets Ben do the climbing course since Ben knows how to climb but he falls but Becca tells everyone that Lance greased the wall, making everyone realize that Lance cheated in every game in the Olympian.
Split into simpler sentences: Charlie lets Ben do the climbing course, since Ben knows how to climb, but he falls. However, Becca tells everyone that Lance greased the wall, making everyone realize that Lance cheated in every game in the Olympian.