Good stuff HM,

1. Remember, the music is relaxing and it makes you feel relaxed. But with feelings, if you want to sound more natural, just say it relaxes you instead of it makes you feel relaxed.
2. I know you were taught "take a rest" in school, but I highly recommend not using it. It usually sounds odd to westerners because Korean students use it so broadly. Instead, simply say rest.
3. Other good expressions for you are "a little R&R" and "recharge your batteries." So instead of "I think I need some refreshing time like this" you can say "I need a little R&R" or "I think I need some time to kick back and recharge my batteries." R&R means rest and recuperation. Kick back just means relax.
4. I timed it, and your answer works. If you want to add something, explain what your long day is. For example, after a long day of research/ running around the office/ filing papers…
5. Opportunity is countable, give it an article (an opportunity).

Interesting stuff, I'm sure you did well!

The music I usually listen to is old pop. What I like the most about it is that it makes me feel very relaxed. I can rest while listening to it and turn my mind off without any distractions. Also, listening to old pop music helps me relieve stress and clear my head. Since I spend most of my time studying and working, I think I need some time to kick back and recharge my batteries. For example, when I feel exhausted after a long day of research and studying, I usually listen to old pop and try to relax. It's perfect an opportunity for me to have good rest and I don't think I can do that without listening to old pop music.

Good work on all your fixes! (check the other responses if you haven't already)