main-domain of wordpress keep redirecting to subdomain

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.