Sorry,I can't understand.Can you please speake Chinese?
Sorry, I can not understand ,could you please speak chinese?
understand理解,明白
could you…… 对别人的一种请求,更委婉
Excuse me ,I can't understand you,please speak in chinese
I`m sorry, I can not understand, could you speak Chinese?
I am sorry I did not understand, please speak Chinese, please