@Kieun1 It can take a long time. It varies. You can and should pester them a bit so they don't put your case aside.
But you don't say whether you actually stayed at this place and then filed a complaint afterwards, or left without staying.
If you stayed for the length of your booking, you won't get a refund. If a place is unacceptable, you contact Airbnb to explain why and to cancel and find another place.
You can't just stay at a place and then demand a refund after the fact. All you can do is write a review warning other guests about the listing.