@Kenza15
You can leave a Response to Review up to 30 Days after the Review was posted.
You can access this facility in a couple of ways.
1) If you have kept the email from Airbnb informing Guest left the Review, it gives you the option to write a Response.
2) On your Dashboard go to HELP.
'Search by Keyword': type 'Response to Review'
2 options in blue appear under 'Recommended Actions'
2nd option 'Leave A Review'
This will take you to your Reviews, and if it's within 30 Days of the Review, under it is written 'Leave a Public Response'