"It's yYou deserve it," they said.

But I knew it' was false, because I slept earlier than most people.

Hitherto, it was a trouble that besettroubled me for many years.

Initially, I guessed that the reason for it was, the accumulation of academic pressure and the lack of nutrition.

When I went to the university, I hadidn't so stronghave any more academic pressure any more rather than high seniorthan when I was in high school.

I supplied much nutrition and simply drankhad a nourishing diet and drank only purified bottled water instead of beverage; Is. I would also run for five kilometers in the playground after the evening study class every day.

Every once in a while, I would go to the barber shop to have a haircut to cut my white hair.

There were numerous white hairs behindon the back of my head.

InFrom other's angle of view, most peopleperspective, they thought Ime stayeding up late and developed unhealthy habits were the caused of it.

"It's what you deserve," they said.

But I kneow it's false because Ithat this is false, since I go to sleept earlier than most people.

Initially, I guessed that the reason was thean accumulation of academic pressure and thea lack of nutrition.

When I went to the university, I hadn't so strong academic pressure any more rather than high senior school.

I supplied much nutrition and simply drank purified bottled water instead of a beverage; I ruan for five kilometers in the playground after the evening study classes every day.

Every once in a while, I would go to the barber shop to have a haircut to cut my white hair.

After a long time, the god gagod had given me a response that made me despair, and she saidsaying, "it simply doeswon't work for your white hair.

But recently, ithings have begun to changed.

There were numerousmany white hairs behindon my head.

In other's angle of view, mMost people thought I stayed up late and developedmy unhealthy habits caused it.

"It's yYou deserve it," they said.

But I knew it's fals wasn't true because I slept earlier than most people.

Hitherto, iIt was a tproublem that besetothered me for many years.

Very formal sounding

Initially, I guessed that the reason was the accumulation of academic pressure and themy lack of nutrition.

Still a little formal sounding but more reasonable for conversation

When I went to the university, I hadn't so stronghad any academic pressure any more rather thanintense than being a high senior school.

In american English "university" would be replaced with "college"

I supplied much nutrition and simplyate healthy and drank purified bottled water instead of other beverages; I ruan for five kilometers in the playground after themy evening study class every day.

Every once in a while, I go to the barber shop to have a haircut to cut my white hair.

After a long time, the god gave me a response that made me despair, and she said, "it simply doesn't work for your white hair.

The Guess OMystery of My White Hair

What you are describing is a mystery rather than a guess. Title capitalization rules usually mean capitalizing every word, but not always. Small words such as "of" are often left lowercase. I recommend referencing an official guide for the subject (if you are interested), I couldn't explain it to you properly.

There were always numerous white hairs behind my head.

Simply writing "There were..." implies that this is no longer the case; the white hairs are gone. But to say you've had these white hairs for a long time, you have a few options:

There were always numerous white hairs behind my head. --- This version implies you've had the white hairs since you were a baby.
Since I was about 15, I have had white hairs behind my head. --- I am making up an age here, but you could use this format to reference how long you've had the white hairs.

In other's angle of view, mMost people thought I stayed up late and developed unhealthy habits that caused itmy hair to turn white.

The first isn't natural but it's unnecessary anyway - you can just leave it off. But if you wanted to, you could say "As for the perspective of others,"

"It's you deserveThat's what you get," they said.

This is how someone would commonly express this sentiment.

But I knew it's fals wasn't true because I slept earlier than most people.

You need the past tense here (it's - it wasn't), but also it would be more natural to say "not true" rather than "false."

HithertoIn any case, it was a tproublem that beset meI dealt with for many years.

"Hitherto" is very archaic / old English - you basically never want to use that. You have a huge option of replacements, I chose one here.

Beset is not far behind, it would be considered extremely formal.

Initially, I guessed that the reason was the accumulation of academic pressure and themy lack of nutrition.

When I went to the university, I hadn't so strong less academic pressure any more rather than high seniorcompared to what I experienced during high school.

Hopefully I understood you correctly, that you faced less pressure during university. This would be a clear way to express that.

I supplied much nutritionate healthy and simply drank purified bottled water instead of beverage;other drinks, plus I ruan for five kilometers in the playground after the evening study class every day.

"I supplied much nutrition" doesn't carry much meaning - but I think you mean to say you ate more nutritiously. I connected these sentences with a comma with the word "plus" to avoid repeating "and"

Every once in a while, I go to the barber shop to haveget a haircut to cut my white hair.

We say that we "get" a haircut

After a long time, the god gave me a response that made me despair, and s. She said, "iIt simply doesn't work for your white hair."

You had a god speak to you? :)

"Henceforth/Since then, I was hopeless to that troublin resolving this issue.

Henceforth is another very old fashioned word, but it can be used if you want to. Otherwise, you could use the more common "Since then,"

But recently, it changedthere has been a change recently.

I find this more natural

There were numerous white hairs behindon the back of my head.

In other's angleFrom one point of view, most people thought that the cause was that I stayed up late and developed unhealthy habits caused it.

"It's yYou deserve it," they said.

But I kneow it's falsnot true because I go to sleept earlier than most people.

HithertoPreviously, it was a trouble that besetothered me for many years.

Your words are correct but very formal and old fashioned

When I went to the university, I hadidn't so stronghave any more academic pressure any more rather than high seniorthan in high school.

I supplied muchhad good nutrition and simply drank purified bottled water instead of other beverages; I ruan for five kilometers in the playground after the evening study class every day.

Every once in a while, I go to the barber shop to haveget a haircut to cut my white hair.

After a long time, the god gave me a response that made me despair, and she said,which was: "it simply doesn't work for your white hair."

I'm not quite sure what you mean by the last part - maybe you can explain in another way.

"HenceforthSince then, I was hopeless to that troubleabout this.