"What are you interested in doing in your free time?"
Correction: "What do you like to do in your free time?"
Asking about someone's personality: In the U.S., it's not common to ask about someone's "personality". In the right context, for example if you met someone at a party or if you were on a first date, you could bring up the question about someone's personality through conversation. For example,
"Hi Minh, nice to see you. This party is pretty lively, isn't it? I usually prefer to stay in and watch Netflix. What about your? Are you more extroverted or do you prefer smaller groups?"