Victor took Victor's seat in the theater before the show started.
Explanation:
Pronounsare words that take the place of nouns or noun phrases. Instead of repeating someone's name constantly, we will use certain pronouns. We can use the second sentence as an example. It's not practical or natural to repeat Victor's name over and over again. Instead, we will start using the pronoun<em> he</em> (and its other forms - <em>him, his</em>) after the first time his name is mentioned. That's why the sentence should be written like this:
<em>Victor took </em><u><em>his </em></u><em>seat in the theater before the show started</em>.