For anyone in the same problem follow this procedure
these are the steps to set up a database and a user for that db, never use postgres as the main user for everyday work or for a public site!!!
1: go to a terminal and gain acces like postgres user:
:~$ sudo su postgres -
2: now going to enter postgres client, there are linux commands to create databases and users, but I preffer to do all in the pgsql client, cuz when you go to other OS don't get lost!
3: Change/set the postgres user password:
# ALTER USER postgres WITH ENCRYPTED PASSWORD 'yourhardtoguesspassword';
don' t forget the semicolon at the end of every sentence in the psql client.
4: Create the new database:
# CREATE DATABASE yourdatabase;
5: Create the new user for the database:
#CREATE USER youruser WITH ENCRYPTED PASSWORD 'youruserpassword';
6: Grant All privilegies to youruser in yourdatabase:
# GRANT ALL PRIVILEGES ON DATABASE yourdatabase TO youruser;
from now on user youruser to manage yourdatabase, ans postgres user only to admin all the databases with pgadmin or other software or the psql client.