Andrew: If I have my free time, I watch a movie at theater
Correct: If I have my free time, I watch a movie at the theater.
Explanation: The definite article "the" is used especially before a noun.

Andrew: And then I meet my friends and have a good time like eating delicious food.
Correct: No correction.

Andrew: However, I don't just spend time with playing my friends
Correct: However, I don't just spend all of my time playing with them.
Explanation: The pronoun "them' is the objective case of they. You could use "them" since it is understood that you are referring to your friends.

Andrew: So, I'll plan when I have my free time
Correct: So I'll plan to have new things during my free time.

Andrew:  For example, I'll make my ability upgrade and learn many experience to better my life.
Correct:  For example, I'll spend my time for enhancing my abilities and learn from my experiences to make my life better.

Andrew:  Therefore, it is important to use my free time for my dream
Correct:  Therefore, it is important to use my free time for achieving my dreams.

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Hi, Andrew! Thank you for submitting your homework. That's a good idea. We can definitely improve our lives through paying attention to our goals. Keep soaring, Andrew!

-Teacher Isabel