Can we still expect any feedback from you? Otherwise this thread will be closed.

How can I?
I mean: YOU have chosen some SECRET credentials on your host side when creating the database. So how should I verify whether you made a mistake while entereing the same credentials when installing Ossn?

can you help me fix this?

Ok, I just had a look onto your site:
the database connection can't be established!
So, open the file configurations/ossn.config.db.php and verify that

$Ossn->user = 'your_database_user'

and

$Ossn->password = 'your_database_password'

are matching with the credentials you created on your host before installing Ossn.

If you can't find any typos make sure that your database user has been granted ALL permissions

Please follow case A here https://www.opensource-socialnetwork.org/wiki/view/1101/how-to-report-a-bug-error