Hello Bongju! ^^

Welcome to italki.com. I hope your English skills would improve here. ^^

~Charlie

Hello. I am newbie.

>> Hello. I am a newbie.

I am newbie in this place.

>> I am a newbie here.

I live in Korean. I graduate University and majored in computer science.

>> I live in Korea and I graduated from university majoring in computer science.

>> OR: I live in Korea and I graduated computer science in university.

I wanna find someone to help study each other.
I can help you to study korean.
>> I would like to find someone who would study with me. I can help you study Korean.

If you're speak English and study Korean, please contact me.
Thank you.

>> If you speak English and you're studying Korean, please contact me. Thank you.

I am newbie in this place.

>> I would say, "I am new to this site."  If you're going to write it the way that you did, you need the article "a" before "newbie."  "I am a newbie."  "A" tells us that there is one of you, and is more general than "the," which would suggest you are either the only newbie here, or the newbie of newbies.  Instead of "in this place," I would say "here."  It's a website.  It's not really a place, and you can't be physically in it.  "Here" doesn't require a tricky preposition in this sentence.

I live in Korean.

>>"Korean" is an adjective.  It's modifies a noun.  "Korea" is the country in which you live. 

I graduate University and majored in computer science.

>> Since your graduation has already happened, you need the past tense "graduated."  It might make more sense to say, "I graduated from University with a computer science major," or, "I graduated from University.  My major was computer science."  Either connect them with a preposition that shows how they are related, or separate them completely into two different thoughts.

I wanna find someone to help study each other.

>>I'm not certain if you were intentionally being casual when you used "wanna."  I would use that texting with my friends.  I would not use it in any sort of business or school writing.  Also, the "each other" needs to come before the "study," otherwise, you're suggesting you and your language partner will be studying one another, not the languages.  It should look like, "I want to find someone so that we can help each other study." "So that" is a conjunction that connects the idea that you're looking for someone with why you are looking for that person. 

I can help you to study korean.

>>Other than "Korean" needing to start with a capital letter, this is okay.  It could also be written as, "I can help you study Korean."  The "to" is not necessary here, and most native speakers would not use it.

If you're speak English and study Korean, please contact me.

>> "You're" means "you are."  There is no need for the "are" here.  I would write this as, "If you speak English are studying Korean, please contact me."  I would use "are studying" because it is the present continuous tense, and you are looking for someone who is currently in the process of studying Korean and plans to keep studying it in the near future.

Thank you.

>>Despite the fact that I made a lot of comments, this was really good.  Your message was clearly conveyed, and that is really important.  Every suggestion I made was purely about grammar.  Keep going! You're doing really well.