WordPress showing error please help

kindly help..wordpree showing this when editing and also mailchimp saying 503 service not available

Error establishing a database connection

This either means that the username and password information in your wp-config.php file is incorrect or we can’t contact the database server at db780949652.hosting-data.io. This could mean your host’s database server is down.

Are you sure you have the correct username and password?
Are you sure that you have typed the correct hostname?
Are you sure that the database server is running?

If you’re unsure what these terms mean you should probably contact your host. If you still need help you can always visit the WordPress Support Forums.

The page I need help with: [log in to see the link]