So I wanted to make ithem better, and that's how ¶
much I wanted to make it a job.

You're referring to "videos", which is plural, so it should be "them" and not "it".

While watching various artists' music videos, movies, and animations, I decided that I'll become a person who produces ¶
videos laterin the future.

(1) Your original sentence doesn't make complete sense. An action, such as the act of deciding, is expected with "while".
(2) "In the future" conveys a longer time period and is more appropriate here. Typically, "later" is used for much shorter time frames, such as in the phrase "I'll do my homework later at night."

Also, as much as I want to work busy at a famous design company, and I hope it will be a future ¶
job.

(1) "As much as" is a grammatical structure similar to "despite" or "even though". It's used in situations where you have contrasting information. Consider the sentence "As much as I want to work overseas, I don't have the money to do so." Here, we see a contrast between between desire and financial ability. However, we don't see something like this in your original sentence, so "as much as" shouldn't be used.

(2) "To work busy at" isn't an expression we use. We'd just say "to work at".

Which group to join was what I was trying to decidinge on.

(1) While your original sentence isn't necessarily wrong, I think "decide on" conveys a greater sense of finality or certainty. I'd suggest "try to decide on", which is more uncertain.
(2) Alternatively: "I was trying to decide on which group to join." This expression might be more common.

dDid you use to cook food when you were in high school?

Mind the capitalisation.

If you’re free, (do you) want to watch it together?

Omitting the subject "you" and saying "want to watch it together" is more colloquial. Since you're writing conversation, I might be acceptable here, but adding "do you" would be the more grammatical expression.

A: He might be at the studio around 5 p.m. ¶
B: rReally?

A: I used to not be the team leader.

Alternatively, and perhaps more naturally: "I didn't use to be the team leader."

A: we’We'd better check the cooking tools and ingredients before the cooking show starts.

Using "the" would be more natural here, since you're referring to the tools and ingredients used for the cooking show specifically.

A: I contacted 30 people, but most of them couldn't come.

"But" implies contrasting information. The expectation would be that all of them would come, so the contrasting information is that most couldn't. If you'd indeed meant to say that most could come, you wouldn't use "but": "I contacted 30 people, and most of them could come."

The fFirst, I often feel uncomfortable ¶
because the shopping mall gets too crowded with too many people.

Alternatively: "The first is (that) I often feel uncomfortable..."

Especially when I have to wait too long ¶
in a line, I hesitate to buy.

aAnd then when it’s too hot or I shop for a long time, I get tired and can’t keep shopping.

Capitalisation.

If they give directions in too unfriendly directionsa way when I ask where ¶
something is, I have to ask again.

"Unfriendly" is an adjective. If you want to use it to modify a verb like "give directions", you can use the structure "in a [adjective] way". If you want to use "too" in the structure, it becomes "in too [adjective] a way", though this might be more advanced.

Lastly, it is inconvenient when there are not enoughthe items I want to buy.

(1) "There are not enough items I want to buy" might moreso be interpreted to mean that you don't buy enough items, and so you want to buy more.
(2) The "the" before "items" indicates that you're referring to the items you're trying to buy specifically, rather than items in general that you happen to come across and want to buy.

finally, I prefer online shopping.

It is odd to use both "lastly" and "finally", since both indicate the final item. I'd remove "finally" here, especially because you preferring online shopping isn't exactly something that bothers you about shopping in the first place.

I was watching a movie with my family and talking about ithe movie when my friend called, so I answered the phone.

I'd suggest replacing the second "movie" with "it" to avoid unnecessary repetition of "movie".

Sometimes, I end up buying too many item s.¶
6) What will your life be like if you live alone?

If I live alone, I may live a relaxed life.,

I'd combine this sentence with the next one. I have replaced the period with a comma to allow for this.

BuHowever, I realized that the videos that got goodreceived positive reactions made me feel proud.

So I wanted to make it better, andso that's how ¶
much I wanted to I could make it a jobcareer.

WhileBy watching various artists' music videos, movies, and animations, I'll hope to become a person who produces ¶
videos latervideo producer in the future.

Also, as much as I want to work busy at a famous design company, I hope it will be a future ¶
job.

I'm not sure what the meaning is here. Could you clarify?