@Linda3345 Once a person sends a request to book, your calendar is blocked for that person. The only way to clear your calendar is to decline the request to book, and, yes, you are penalized for declining booking requests. You have 24 hours to accept or decline a request to book.
You could, of course, decline the request to book, which would free up your calendar, and then contact the person who inquired, but you have no guarantee the inquiry would turn into a booking, and you could end up with nothing.
You could also try asking the guest to withdraw the request to book, if you have a good reason for it - for example, if you find out they are not a good fit for the space, or they request an amenity you don't have.
I think it's best to keep a firm booking - first come, first served - and not wait for people to make up their minds what they want to do, or play around for longer bookings.
If you don't want to accept 2-day stays in the future, you can change your settings to a longer minimum stay. You never want to cancel a booking.
Also, since you are new, it doesn't hurt to take a few shorter stays until you get more comfortable with hosting, and build your reviews.