As a result, I neemaded to move it tohe appointment for tomorrow.

I have to do it as soon as possible because I almost have a waist-length hair.

There is a custom in my country that people who have a waist-length hair need to find a special day to have her hair cut, because this such long hair would havecontain a spirit and it will getfeel pain if they don't choose a proper day.

Someone sayid if you don't follow it, you will be down on your luck.

I don't want this thing to become a troublesome, so I'd better finish it quickly.

I have to do it as soon as possible because I almost have a waist-length hair.

This is more natural in the US:

I have to do it as soon as possible because my hair is almost to my waist.

There is a custom in my country thatwhere people who have a waist-length hair need to find a special day to have their hair cut, because this such long hair wouldhair this long will have spirit and it will get pain if they don't choose a proper dayexperience pain if a proper day is not chosen.

Wow! I hadn't heard this before. Very interesting.

Someone say that if you don't follow it, you will be down on your luck.

or

Some say that if you don't follow it, you will have bad luck.

I don't want this thing to become a troublnuisance, so I'd better finishcut it quickly.

or

I don't want this thing to become a bother, so I'd better cut it quickly.

Today I planned to haveget my hair cut, but I didn't make an appointment in advance.

This sounds more natural.

There is a custom in my country that people who have a waist-length hair need to find a special day to have their hair cut, because this such long of hair would have a spirit and it will getfeel pain if they don't choose a proper day.

This sounds a bit more natural: There is a custom in my country that people who have waist-length hair need to find a special day to have their hair cut, because this long of hair has a spirit and would feel pan if a proper day isn't chosen.

Someone sayid if you don't follow ithis rule, you will be down on your luck.

I don't want this thing to become a troubln issue, so I'd better finish it quicklycut it soon.

Unfortunately, it wais Sunday and nearclose to Chinese New Year.

Because you’re writing something factual about the present moment, you can use the present tense.

I have to do it as soon as possible because I almost have ahave nearly waist-length hair.

Hair is a mass noun in English (i.e. not countable), so you don’t need the indefinite article “a” in this sentence.

“almost” and “nearly” have more or less the same meaning, but the use of nearly often coincides with measurable or otherwise numerical information (in this case, the length of your hair!)

ThereIn my country, it is a custom in my country thatary for people who have a waist-length hair need to findto designate a special day to have their hair cut, because this(it is believed that) such long hair would have(attracts) spirits and it will getbe painful if they don't choose a proper day.

Same correction as above re: hair.

the appropriate personal pronoun corresponding to “people” in number and gender would be “their”. You could also rewrite the sentence to say something like: “a person who has waist-length hair needs to find a special day to have their hair cut….”

Someone say that if you don't follow (or: heed) it, you will be down on your luck.

heed = to pay careful attention to something (i.e. warning, advice).

I don't want this thingmy hair to become a trouble(or: a pain, a burden, an inconvenience), so I'd better finish iget it cut quickly.

“a trouble” sounds a bit funny in this context. Here are some more natural-sounding alternatives.