And sSome countries in Asia also have the festival such as: China,Singapore,Japan...[Technically, a sentence should never be started with the word "and." It is done sometimes, however, in very informal communication such as blogs (like yours...) and text messsages.]

However, when you expected too much from something, it would be opposite. [Perhaps try: "...you may receive the opposite."]

This thing was true for me :( .

That subject is so hard for my friends and me because we had to study in english with a lot of new vocabulary words. [There is only one vocabulary that is composed of many words]

In addition, it took 4 hours per week to attend this class as well as to find out more about the subject.

Unfortunately, I was a little sick too.

That's why I decided to stay at home to enjoy the rest of the day.

It makes me feel peace [around and in my mind as well] There is nothing grammatically incorrect about the phrase "around and in my mind, but it is awkward. A common English phrase used to describe what you are saying overall is, "It gives me a sense of peace."].

Moreover, I ate a piece of a mooncake and drank a cup of tea.

Mooncakes are too sweet, so I don't like to eat much of them.