Hello @Katherin-and-Massimo0
BNB doesn't allow contact betweent guest and host till the guest has book to protect both you as the host and the guest. People have been known to get contact details in order to burgalise a home, harrass you or to try and beat you down on price.
It also protects them as some unscrupulous guests use direct contact to bypass the system and try and pay in cash.
There are other listing that allow contact so if this is an essential for you, you may be better using them.
I am sure you have already had a look around the information BNB provides for hosts and its help section, but a few things
1. Only take verified guests who have provided BNB with photo and social media ID
2. Only take guests with previous reviews - but you will severely limit your guests as most are new to BNB
3. Make sure your guest have a photo and description on their profile and that they tell you about their plans and why they chose your place (don't have instant book turned on so you can chat via messaging before confirming a booking).
4. If you don't feel comfortable decline.
Check out the community guides here too on the Community Help forum.