I feel even better now after today’s English exams, even though I didn’t attend the last one because it was too hard for me to pass so. Therefore, I thought I willould take that exam next year with good preparation.

This sentence feels very run-on. Put in some punctuation and broke up the structure a bit to make it less of a drag to read - this would be a pain to say out loud without any pauses. "Although" is an alternative to "even though".
I would use the conditional when using the past version of "to think", the alternative here would be "I think I will" - which keeps everything consistent.

I must be well prepared in aby next year, or I will have to wait foryet another year for the once-a-year opportunity for it, which for me isto take it again. That would be so time-consuming for me.

This all makes sense, but it feels redundant with how much you use "year". I would advise cleaning it up and reiterating instead on what you have to would have to wait another year to take. "Wait for another year" is understandable, but feels wrong.
"By next year" sounds better than "in a year" when used with "must".
Switched the order of the last sentence, because it sounds more natural.
Split up the sentences to avoid a run-on again, and changed "is" to "would be", because the event you are speaking of has not occurred yet, nor is it guaranteed to occur. Therefore the conditional is used because you are unsure if you will have to or not.

I have been doing my daily routines, namely that include brushing my teeth, washing my face, and exercising on a regular bases, and tis. This is very good for me to, because I can cultivate a good mood during the day and to keep myself clean and fresh throughout the whole day.

I changed up the start of the sentence to make it sound a bit more concise. I do not think specifying that they are *your* daily routines are necessary, as it is implied within the context.
I'm not a fan of the usage of the word "bases", but I am proud of the effort.
When splitting up the sentences, I removed "and" because it is unnecessary. "Very good for me to cultivate" sounds wrong. I read it a few times over and even though it's well understandable and by no means bad, it just didn't feel right.

I would have been done so long back thenago, but due to the lack of sleep, caused by heavytoo much homework, I did not have a single bit of energy to keep myself clean and tidy, s. Seriously, not a singlone!

"been" is necessary when joining "would have" with a past participle.
"ago" works better than "back then" here, I think.
I changed "heavy" to "too much" though I wouldn't hate the usage of "a heavy amount of homework" - I think "too much" is a simpler solution.
"Not a single" doesn't work. I rephrased it to what I think you had intended here.

It was so tough that I had to get up around 6:30 in the morning and still not get my homework done until midnight.

I think using "until" in this case sounds better with the negative. "Until" in my mind sounds it needs an action in progress - where "get my homework done" in this context sounds like the completed action.

I hate being in a typical Chinese school;, and I wish I could have been born in another good country;. I regret the fact that I did not know what a normal and happy life could have been.

I think you should use "the fact that" with regret, it's much more common, or even just "that"
"I regret that.." or "I regret the fact that.." sounds better.
I appreciate the attempt to use semicolons here, but I don't know if they work.

I dislike some of the teachers I had in school, and I look down on most Chinese teachers and professors for they are not competent in academic teaching and they cannot educate me intoso I can be the person I’ve always wanted to be.

"into" sounds wrong. I used "so I can be", because I think it fits with your message.

Luckily, after more than 4four years since I left school, with my energy boosted and fatigue fading away, I am on my way to becoming the person that is in my heart.

Simple numbers should be written out, in my opinion.
I think adding "that is" makes the sentence sound cleaner.

Personally, I am sure that I know the world better than most young people, and also that I am more tech-savvy than most middle-aged adults.

I think you should use "that" here. Everything else is good.

We"You only live once", as this popular idiom suggests, - so why do we have to be unhappy only for, yet try to provinge that we are better than others?

Added quotes around the start of the sentence and changed it to the more common version of the idiom.
Got rid of "as", I think it's unnecessary here.
"only for proving" sounds incorrect. "yet try to prove" here I think is slightly poetic and is in line with your messaging.

If someone comments improperly onmakes an inappropriate comment about me, I will tell hithem to MIND YOUTHEIR BUSINESS!

"make an inappropriate comment about" is used a lot and well-known.
Changed pronouns to be more consistent.

Doid you cry when you heard the news that Ukraine was invaded and thousands of people died?

"Did" instead of "do" to keep things in past tense. "You heard" because the you need to specify which person is hearing the news."

I don’t think you willdid if you are normal like everyone else.

Past tense, not future tense for consistency with the prior sentence.

I, as a man who has never been in a relationship with a girl in my life who is 23 this year, may be taken as a clown to be laughed at, saying yYou may laugh at me, someone who will be 23 this year and has not yet had a relationship with a girl. People also say, "You’ve never had one so you don’t know and you will change your mind once you find one".

This is a long, LONG run-on sentence. The "I, as a" structure is well-known in English, but this is simply too long for it to function in its intended purpose.
I instead opted for a different sentence structure to allow to allow things to breathe. This may be the most distant sentence from what you had written yet - but I believe it to be close enough while being less jumbled.

Following Chinese traditions and being gifted, or to say,in other words - cursed by a general Chinese personality, is good in some cases, but. However, it happened not to be my requirement for the other half of..

At the start of the sentence I wasn't sure what you were implying - so I went with what I thought made the most sense. I will leave an alternative here and I'm sorry if I had misread your intent.
I took it that you meant to say that your general Chinese traits are like a double-edged sword, a blessing and a curse.
If you meant that instead you were cursed by a general Chinese personality despite these traits, I would use: "Following Chinese traditions and being gifted, though cursed by a general Chinese personality.."

I changed the sentence once more to not be a run-on, but I was just so confused by what the second part of this sentence was supposed to mean.
I felt as though the other half was not specified, so I left it off on a set of trailing ellipses.
If the other half *was* specified earlier and I didn't see it, then this would be correct without "of" at the end, but seeing as I did not see anything that would bring this together.