I am from china,i like english,

1. Either separate your sentences or add "and".  In other words: "I am from China.  I like English, and I think that learning English well..." 

i think learn english well is very good to communicate with foreigner and a better understanding of the world.  --> I think learning English well is very important for communicating with foreigners and getting a better understanding of the world.

1. Learn應該是Learning，因為你需要的是一個 noun clause.  In Chinese, one might write 我認為要跟外國人交流就得掌握英文; there is no change to the verb phrase 掌握英文。  However, in English, you need a noun clause (名詞性從句) after the "I think..."  After all, you are thinking about SOMETHING.  同樣的，Communicate應該是communicating.

2. Foreigner --> foreigners (不要忘記，當你大體上談論事情的時候，應該用複數名詞，比如說 I like cookies.  I hate Mondays.  He enjoys reading books.)

3. Love english but not learn a good. --> I love English but I'm not learning too well.  英文跟中文不同，主語是不可省略的。

從這三點開始研究吧！  ^__^.