如果别人对我说英语，但我听不懂，我应该用哪句英语回答呢？

尊敬,委婉的说法是:
Pardon?
I beg your pardon?

随意,偏口语的说法是:
What did you said just now ?
Wait ! I can't follow you ,can you just slow down ?

实在听不懂的话,可以谦虚地说:
Well,I missed it again ,I think I have a long way to go.

Sorry,I don't understand.Can you speak Chinese?

简单的一句，I’m sorry。不就完了

第一次。说.....sorry？对方会重复
再听不懂.....Can you please say it again？
再一次... sorry.. I really can not understand you..

常规
pardon？
i beg your pardon?

如果听不懂但是还想拽一下
sorry，i can't follow you
sorry,i can't get your meanings

故意拽
sorry，that's beyond my comprehensive

第一次的话 就说个 Pardon? 然后人家就会重复 然后如果还是听不懂的话就I'm sorry but I can't understand you.