Database user/password hurdle

Nextcloud version (eg, 10.0.2): 12.0.4
Operating system and version (eg, Ubuntu 16.04): Raspbian Stretch
Apache or nginx version (eg, Apache 2.4.25): Nginx 1.10.3
PHP version (eg, 5.6): PHP7.0

The issue you are facing:
Cant seem to get pass the Installation wizard. Always encountered
`Error while trying to create admin user: Failed to connect to the database: An exception occured in driver: SQLSTATE[08006][7] FATAL: password authentication failed for user “postgres” FATAL: password authentication failed for user “postgres”

Here is the inputs for the fields:
Username: PBJ
Password: pbjsw
Data Folder: /var/www/nextcloud/data
Database user: postgres
Database password: pbjsw
Database name: pbj_cloud
Database host: localhost:5432

I have a postgres user with ownership to the database name in my postgresql.

Following the instructions from

"After you enter your root or administrator login for your database, the installer creates a special database user with privileges limited to the Nextcloud database. Then Nextcloud needs only the special Nextcloud database user, and drops the root dB login. This user is named for your Nextcloud admin user, with an oc_ prefix, and then given a random password. The Nextcloud database user and password are written into config.php:

‘dbuser’ => ‘oc_molly’,
‘dbpassword’ => ‘pX65Ty5DrHQkYPE5HRsDvyFHlZZHcm’, "

I realised the config.php file has already been customied to what I enter and now I cant create a database.