@Yvette-And-Martin0
Be clear with the party checking out that they must have vacated their room by xx hrs and do this up front as part of the booking process. Explain that you have other guests arriving and need to turnaround the room/property.
Be clear with your arriving guests whether or not their place will be ready when they check in. If they are arriving on an early flight for example, you may be happy to explain you have guests the previous night, happy to take their cases and give them a key and their room will be ready at xx hours. Make sure you phrase it as: you can drop off your bags and I will give you a key so you can go out exploaring while your room is being prepared - so that they do not expect to sit around for a few hours.