a few sentences

1. At what age do most people get married in your country? Corrections: word choice (using the correct word) , word order (placement of words in the sentence) and punctuation (using a capital letter to start a sentence).

2.you looks like very love the cat.aren't you？

2a. You really love the cat. This is a statement. It is used for stating a fact (when you know for sure)

2b. You really love the cat , don't you?This is a question. It is used when enquiring about the truth (when you don't know for sure)

A sentence has to be a either a statement or a question. It cannot be both at the same time. You have to choose which is more appropriate for your sentence. If you know for sure that the person loves the cat, you would use the statement. If you don't know for sure, then you would choose the question.

3.there's a fairly magical story happened at me

3. A fairly magical thing happened to me.  "There's" is the wrong word to use here. Also your story happens to you not at you. "There" and "at" suggests the story happened to someone else. So you should say "My magical story..." because it is you're story.

4.i can't sleep until now.my dad n my mon eithernow.cause my dog is always barking

4.  My parents and I can't sleep because my dog is always barking. When referring to other people (your Mum/Mom and Dad), always put them first (eg: My friends and I... My parents and I...) This also removes the need to repeat yourself (specifying who can't sleep in different sentences). 

5.i don't know what can i do now.i just know that i must go sleep now.and the day after day still nice.everyone are fine.include me.

5. I don't know what I can do to help me sleep now. This is only a small problem though, because everyday is still nice and everyone is fine including me. There is no need to repeat yourself and it is confusing to read. 

6.So did u go china study to see beautiful women？（a man who go to the china to study .because he can look many beautiful girls）

6. Did you study in China to see beautiful women? (Many men go to study in China because they can look at many beautiful women) Word choice 

7.the book on the tale are what u want.isn't it？

7. The book about tales is what you want, isn't it? Punctuation (capital letter to start). Avoid repeating yourself (the) Choose another word for this.

8.dear me . why don't your school haven't Chinese course

8. Dear me, why doesn't you're school have a Chinese course? Punctuation (capital letter to start and question mark to end). Double negative in this is using "don't" and "haven't". They cannot go in the same sentence. Doesn't is short for "Does not"