Complex sentence: During the trial, Four admits that he joined Dauntless to escape his father's abuse, and that he was going to leave Dauntless to be factionless after this last group of initiates, but he saw Tris and decided to protect her.
Split into simpler sentences: During the trial, Four admits he joined Dauntless to escape his father's abuse. He intended to leave Dauntless to be factionless after this last group of initiates, but saw Tris and decided to protect her.