Complex sentence: On career day, Stuart Minkus, who turns out to be Farkle's father, visits their school and a battle ensues between him and Topanga, an ongoing battle since childhood to be the smartest in the class.
Split into simpler sentences: On career day, Stuart Minkus turns out to be Farkle's father, and visits their school. A battle ensues between him and Topanga, an ongoing battle since childhood to be the smartest in the class.