happyvanchai
I do not want to appear to be discriminatory here, but I must assume you are of Chinese origin, and that English is not your native language.
I understand English is not the easiest language to learn for non native English speakers. I have a problem with memorising because it means you most likely do not fully understand the meanings of the words (phrases) that you are putting together, and therefore not fully understanding what information you are trying to convey.
Therefore when a different situation arises that was not in the course sim you will not know what to say to extract the information you require because it was not memorised and you will not be able to ad lib (make it up as you go) when required.
Your best bet is for you and your friends to surround yourself with native English speakers (preferably who are in aviation related disciplines) for as long and as often as required until you feel totally comfortable with English
Cheers