How To Reinstall WordPress Core Files
Step 1 - Download the latest version of WordPress from https://wordpress.org/download/
Step 2 - Use the cPanel File Manager to upload the WordPress zip file into the public_html folder (click here for a guide)
Step 3 - Use the cPanel File Manager to find the file titled wp-config.php and rename it to wp-config.php.real
NOTE: If you are doing this because your WordPress site is hacked, delete all files except the wp-config.php.real .htaccess and wp-content
Step 4 - Right click on the WordPress .zip file in the cPanel File Manager, extract the files and overwrite any other files if it asks
Step 5 - Delete the wp-config file in public_html then rename the wp-config.php.real file back to wp-config.php
If the steps didn't follow properly and something broke, click here for our guide on restoring your website using our automated backups