This is a buddypress page, linked with the page ID 4275. The body class of your delivered HTML is:
<body class="registration register buddypress page page-id-4275 page-template-default admin-bar no-customize-support no-js">
To edit this page itself, go to http://hoteliersnetworkme.com/wp-admin/post.php?post=4275&action=edit
BuddyPress filters the content of this page and adds a registration form.
To modify the registration form itself, please refer to the BuddyPress documentation.
BTW: Seems like you have got a lot of work to do, cleaning all this up. Just at glancing at it I found 36 stylesheets and 61 Javascript files, as well as inline scripts, from at least 22 plugins plus your theme and child theme..