In KOREA, I think that there are three kinds of famous SNS service. Facebook, twitter. instagram. Then, My favorite SNS service is facebook. because It has the most users than other SNS service. also most of my friend uses facebook. it can treat more contents than twitter. i don't have a information about instagram. i usually posted picture that i shot in outskirt, but i don't like a posted picture that otherpeople had taken me. Using SNS has Advantages. It can help maintain friendship by writing little comment or clicking a LIKE button. and you can know friend's recent condition by watching his posting. so you can easily communicate your frined.

CORRECTIONS:

In KOREA, I think that there are three kinds of famous SNS service. Facebook, twitter. instagram.

-- > In Korea, there are three most used SNS; Facebook, Twitter and Instagram.

Note: Use the right punctuation marks, when you are trying to enumerate things, you can use the ";" semicolon.

Then, My favorite SNS service is facebook. because It has the most users than other SNS service. also most of my friend uses facebook. it can treat more contents than twitter.

--> My favorite kind of SNS is Facebook because it has the a lot of users compare to other type of SNS. Most of my friends use facebook, it has also more contents than twitter.

Note: Do not use period if it is not needed, make the sentence complete.

I don't have a information about instagram. i usually posted picture that i shot in outskirt, but i don't like a posted picture that otherpeople had taken me.

-->I don't have much information about Instagram, I usually post a picture that I taken but I don't like the pictures that other people had taken from me. 

Note: Use the right article or conjunction.

Using SNS has Advantages. It can help maintain friendship by writing little comment or clicking a LIKE button. and you can know friend's recent condition by watching his posting. so you can easily communicate your frined.

-->There are many advantages of SNS; it can help you to be updated with your friends' recent activites through their posts and you can also communicate with them. You can put a comment to their posts and click the like button if you want.

Note: Make sure that the sentence is understandable, using a lot of periods (.) is not necessary.

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 In Korea, there are three most used SNS; Facebook, Twitter and Instagram. My favorite kind of SNS is Facebook because it has the a lot of users compare to other type of SNS. Most of my friends use facebook, it has also more contents than twitter. I don't have much information about Instagram, I usually post a picture that I taken but I don't like the pictures that other people had taken from me. There are many advantages of SNS; it can help you to be updated with your friends' recent activites through their posts and you can also communicate with them. You can put a comment to their posts and click the like button if you want.

Thank you!