yao978318542 You deleted the database in MySQL/MariaDB (through your site control panel or phpMyAdmin) somehow? If that's true, then there's not really a way to fix it, all the Flarum data is stored in there. Unless you have it backed up, it's gone.
But, you might have simply deleted the config.php file. Check your databases through your host's control panel or phpMyAdmin (however you set it up on install) and see if Flarum's is still there with data. If the database is still there, we can fix the missing config.php file.
