For your amusement:
Dui bu qi, wo bu dong= I'm sorry, I don't understand.
Ting bu dong= I heard what you said but I don't understand.
Zhongwen zenme shuo?= How do you say that in Chinese?
Wo zhende buzhidao zenmeshuo. I really don't know how to say that.
Wo yao waidai.=I want take out.
Bu yao. =I don't want (whatever they're offering).
Yi bei re kafei. Bu yao nai, bu yao tang.= One cup of hot coffee, I don't want milk or sugar.