因为你没有英语的环境.

正如輔助小姐(Ms Help)所說的，這就是學習一門語言的關鍵，那就是妳需要在一個妳必定要用上該門語言的環境以下慢慢地學習、訓練和應用；這樣妳才能強迫自己用上該門語言作溝通和交流，以及把那門語言學得更好和更有進步。相反，若妳活在一個可以用回自己母語的環境下學習，那麼只要遇上甚麼問題和挫折，妳便不以為然地用回自身的母語來表達；學習效果當然大打折扣。 其實妳現在所想的疑惑，也許跟一位在英語國家長大的華裔人士所想的差不多：「為甚麼我在外地學了十幾年的中文竟然比不上一位華人到英語國家學習一兩年的英語好？」所以請不要氣餒；反之應繼續努力學習、充實人生。 祝　是日安好。 Good day.

People who learn English are concentrating on grammar and their thinking were still in Chinese. Eventhough what the sentences were correctly constructed but it isn't the way what the English speaking people used to say. English speaking people living in China, they speak the way what the Chinese people would say and they repeat the same sentences or expressions everyday. For example, peanut butter, I pronounce "peanut budda", it is the wrong pronounciation in China. But, if you live in the United State, you will pronounce peanut budda instead of peanut butter. same token, people living in China, they learned how to pronounce the words or sentences correctly, sounds like native.

如果换个方向思考，如果你在中国学5年的英语，可能不如你在美国生活一年的学习效果好。因为你整个一年都是泡在英语环境里。而你在中国学习5年总共使用英语的时间其实并不超过1年。

Without daily exposure learning a language is very hard. As many Chinese students don't have the ability to practice the way you would if you could go abroad, it is best to replace this with frequent forum (BBS) visits, and tv-shows. This will balance out the grammar-focused Chinese education system and give you some idea of how "real" English is spoken. I want to add though that there are dozens of foreigners in China who barely speak any Chinese, even after several years. It's a combination of studying and being surrounded by it, not just one of the two. Study hard in school and surround yourself at home by visiting English websites, and watching English news and tv-shows.