@Cristiano155 Instant Book means a guest simply books without a host's approval. You don't get a chance to read their reviews nor communicate with them before their booking is confirmed.
If you don't want that, turn off Instant Book. If you want to leave it on, make sure to choose the requirements available to you for IB guests.
I suggest you take some time to read through all the articles for hosts on the Help section of the main Airbnb site.
If you don't understand the difference between IB, requests, and inquiries, or how cancellations work, there are probably other things that you'll get caught out on.
It's a big learning curve, so study up as much as you can.