According to the Codex instructions:
https://codex.wordpress.org/Changing_The_Site_URL
If you add these defines to your wp-config.php
define( 'WP_HOME', 'http://example.com' );
define( 'WP_SITEURL', 'http://example.com' );
These will override the options saved in your wp_options table, you should then remove the /NewSite suffix from your General Settings page. (Or if wp-admin is accessible now you may be able to just do that already.)
Alternatively you could edit the database directly and change the home and siteurl values in wp_options and that will achieve the same thing.