Hello, Kirby! Thank you for passing your homework. I see you do fun things
on Fridays that's why it's your favorite day. I bet you are already looking
forward for this Friday! Here are the corrections to your composition. Kindly read and study them. If you have any questions, feel free to ask me in class. Thank you, Kirby!

~ Teacher Mary

My favorite day of the week is Friday.
Explanation:
a. Since you are talking about one day, which is Friday, we should put day instead of days.
b. Friday is a proper noun so its first letter should be in big letter.

Because on Fridays, I can play with my friends for a longer time than any other days.
Explanation:
a. We should use the preposition on before the word Friday. This preposition is used before exact dates or the days of the week.
b. We write Fridays instead of just Friday because you do those things every Friday and not just on one Friday.
c. Since you are comparing Friday with other days, we write longer instead
of just long.

My friends and I play video games and do many things.
Explanation:
a. There is no need to put a comma after I.
b. We add the word do because if it's just many things, it doesn't make the
phrase complete.

When I come back home, I become unhappy.
Explanation:
a. It is more appropriate to use the conjunction when in this sentence.
b. Since you play with your friends and you come back home every Friday,
we should write come instead of came.

Because, I need to wait for a long time to play with my friends again.