can't create a local server

Hi all!

This is my first to the list.

Using pgadmin4 I can't create a local server "timeot expired"
from debian buster terminal ask me to verify I'm allowed to connect to the unix domain socket /var/run/postgresql/.s.PGSQL.5432

su

Password:

root(at)mycomputer:/home/me# su - postgres

postgres(at)mycomputer:~$ psql

psql: error: could not connect to server:

File o directory non esistente Verifica che il server locale sia in funzione e che accetti connessioni sul socket di dominio Unix "/var/run/postgresql/.s.PGSQL.5432"

I solved this problem with postgresql10 modifying a .conf file but file and directory names changed in postgresql 12

Can you help me?

Thank you in advance