對住一個外國人~如何用英文表達"以後就麻煩你了"

If you really tell him that you will bother him/her in the future. I think he/she will be disappeared immediately from you!!!! Hahaha.

O.K. You may say: I really need your help in the future in this aspect and hope this won't bother you too much time!

中國人講野太多禮貌啦
外國人係唔會甘講野，所以最好唔好照字面直譯。

Thank you for your help in advance.

唔好用 Trouble, Problem 呢的字。 一聽就知你係 Chinlish.............

thank you for helping me, i'm sure i'll need your help in the future. Hope it doesn't bother you.

Thanks in advance for troubling you in future.

Thanks in advance for........

you can say: i am sure i will need to bother you in future.
however, i wonder if they really express this kind of idea in daily conversation. so i only try to translate the meaning. hope this can help.