@Gaby221 One thing you will need to do is review your listing settings. You should specify what your check-in time is, and whether you require advance notice for accepting reservations e.g. "same day up to a cutoff time" or "at least one day's notice"
This has to be set up under "Pricing and Availability" "Calendar Availability" so that the system prevents short-notice bookings. There's also a "Preparation Time" setting that blocks however much time you'd like before and after each reservation e.g. none, one day etc. Writing it in your profile won't prevent people instant booking or sending trip requests at the last minute.
If you don't have enough time to prepare, you can decline a request to book. You don't mention if you have Instant Book switched on. If you do have it switched on (generally by default) all you can do is cancel (not recommended) or try and work with the guest to give you enough time to be ready.