Nicole:The thing I want to do with my sister
Correct: The things I want to do with my sister.
Explanation:Since you're referring to many, you could add -s to indicate plural.

Nicole:I want to do many things with sister.
Correct: I want to do many things with my sister.

Nicole: First,I want to ride a bike with her.
Correct: First,I want to ride a bike with her.

Nicole: After that, My stress goes away and we can be more closer.
Correct: It eliminates my stress and a way to be more closer with her.
Explanation: "Eliminate" means to remove.

Nicole: And secondly, I want to watch movies with her.
Correct: Second, I want to watch movies with her.

Nicole: Me and my sister loves watching movies.
Correct: Me and my sister love watching movies.
Explanation: Basic Principle: Singular subjects need singular verbs; plural subjects need plural
erbs.

Nicole: Lastly, I want to go picnic with her.
Correct: Lastly, I want to go on a picnic with her.

Nicole: We can eat many delicious foods and watch an exciting shows.
Correct: We can eat many delicious food and watch exciting shows.
Explanation: Food is usually uncountable but it can also be countable.
You could say "many types of delicious foods" but not "many delicious foods".

Nicole: I'm happy to think about it.
Correct: These things make me happy whenever I think about them.
Explanation: The pronoun "these" is used to indicate
people, things, or places previously
mentioned.  The pronoun "them' is the objective case of they. You could use "them" since it is understood that you are referring to your friends.

*******************************************
*******************************************

Hello, Nicole! Thank you for submitting your homework. Please do take note of
the corrections that I have made for you. On the other hand, I am glad that
you totally want to spend time with your sister. This means that you really
love her. Great job, Nicole!

-Teacher Isabel