Is there a timeframe I must reply within?
You should respond within 36 hours or the request will be closed automatically. However, it's in your best interest to reply to the message sooner if possible.
The message is from a guest who's interested in staying with you. They need to check if you are available for their dates of travel and maybe ask some specific questions before booking.
The sooner you reply, the greater the chance you’ll get a booking.