Wordpress errors

Error: Fatal Error: Cannot redeclare get_temp_dir() (previously declared in /home/public_html/wp-includes/functions.php:2160) in /home/public_html/wp-admin/includes/file.php on line 189

Solution: Reinstall all WP core files. To keep the plugins, themes and content. Just deleted WP-Admin and uploaded the fresh version and the same for the functions.php.

Source: https://wordpress.org/support/topic/upgrade-from-wp-314-to-wp-32-admin-error-cannot-redeclare-get_temp_dir