Why have to re-install the existing wordpress after deployed on heroku

I have an existing WordPress website that works fine locally and on an online server. I just want to move my website to Heroku.
I have deployed to Heroku by followling this tutorial.

But, when I access to myappname.herokuapp.com, it asks me to reinstall WordPress again. How do I fix this?

I deleted /wp-admin/import.php, /wp-admin/install.php , /wp-admin/install-helper.php, /wp-admin/upgrade.php, and /wp-admin/upgrade-functions.php.

/wp-config.php:

/** This should point to the app directory */
define('WP_SITEURL', "http://" . $_SERVER["HTTP_HOST"]);
/** This is the URL your visitors will see */
define('WP_HOME', "http://" . $_SERVER["HTTP_HOST"]);
define( 'WP_CACHE', true );
define( 'WPLANG', 'vi_VI' );
$url = parse_url(getenv('DATABASE_URL') ? getenv('DATABASE_URL') : getenv('CLEARDB_DATABASE_URL'));
/** The name of the database for WordPress */
define('DB_NAME', trim($url['path'], '/'));
/** MySQL database username */
define('DB_USER', $url['user']);
/** MySQL database password */
define('DB_PASSWORD', $url['pass']);
/** MySQL hostname */
define('DB_HOST', $url['host']);
/** Database Charset to use in creating database tables. */
define('DB_CHARSET', 'utf8');
/** The Database Collate type. Don't change this if in doubt. */
define('DB_COLLATE', '');

/.htaccess:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress