Download the theme again, go to you filemanager in cPanel (or open an ftp client) and simply copy the contents of the fresh header.php from the download into your header.php file in your theme (or upload the new header.php file to your themes directory using the ftp client). This should fix the error there. Keep a copy of Mandigo untouched and unedited so that you can recover if it happens again.
To remove your home link, you will need to remove this section of the code in your header.php file:
<li class="page_item"><a href="<?php echo get_option('home'); ?>/"><?php _e('Home', 'mandigo'); ?></a></li>
I’m not familiar with this theme, and it looks to be filled to the brim with other code, but with that
- tag removed, the only pages that should display from this point on are your ‘pages’ as they should normally.