"我好快返" 英文可以點講?

出門口同另一半講"我好快返架啦", 可以講,

Before you know it

I will be back before you know it. 

仲有其他idioms都係"好快"嘅意思

In the blink of an eye
Monday comes in the blink of an eye.

Split second
Weekend passed in a split second.