Restricting the access to a database

Hi all, im new in this and my question can sound stupid, here is the
thing, i have a server wich have 3 databases, each one with different
users(user1, user2 and user3)

user1 have : db1, db2 and db3
user2 have : example1
and user3 have : pgadmin

Im trying this :

I want that user1 have access only to his databases, and so on,i mean
user1 most not see : example1, pgadmin.

With the schema i resrict this but only on the tables of adatabase, but
if you change search_path and add the user1's schema then you can see
their tables.

Does anyone has done it, or know how to do this??

thanks