your reply is very helpful, thank you very much!

I can understand what you mean. Because I've been facing the same problem when I was learning English. People used to talk to me in English and I could understand what they said but unfortunately I could not reply them because I had to think about what to say, because the English language was not my first language and I was very new to the country(London). However, I have developed speaking English when I met people who always communicated in English although the English language was not their first language. In my opinion, you should meet people in your city that are speaking both English and their mother-tongue. That way you can communicate in both English and Chinese. Hope that helps!