Drupal already installed

[maxsim86]

To start over, you must empty your existing database and copy default.settings.php over settings.php.
To upgrade an existing installation, proceed to the update script.
View your existing site.

what are u thing about this,

[ghost]

It's hard for me to say without seeing more detail, but if you've gone through the instructions in the readme.md and imported the provided database, then it sounds like your issue could be resolved by one of the following:

• Try flushing caches (from web dir, run ../vendor/drush/drush/drush cr)
• Make sure your settings.php is referencing the database you imported to (if it doesn't exist, make settings.php from a copy of default.setting.php and update it)
• Check your directory and file permissions

More info about settings.php and permissions can be found here if you need it.