Access denied for user ‘user’@’localhost’ (using password: YES)

Take a look at docs https://dev.mysql.com/doc/refman/5.7/en/grant.html#grant-database-privileges.

Also try tips in threads at
https://stackoverflow.com/questions/20353402/mysql-access-denied-for-user-testlocalhost-using-password-yes-except-ro

You should also change your database password as soon as you get a chance, because these are public forums, and they are indexed and cached by search engines like Google.

Check wp-config.php file, open in your WordPress directory, and confirm this lines have correct details:
define('DB_NAME', 'your_database_name');
define('DB_USER', 'your_database_user');
define('DB_PASSWORD', 'your_database_password');
define('DB_HOST', 'localhost'); // Confirm this with your hostname or IP

Check that the user specified in wp-config.php has access to the database and has the necessary permissions.

Test Database Connection by creating the test-db.php file:
<?php $link = mysqli_connect('localhost', 'your_database_user', 'your_database_password', 'your_database_name'); if (!$link) { die('Connection failed: ' . mysqli_connect_error()); } echo 'Connected successfully!'; mysqli_close($link); ?>

Upload this and test connection, If the above steps don’t resolve the issue, contact your hosting provider for assistance.