Fix wordpress errors

I’m having an issue trying to fix a problem on WordPress. I have tried to disable all the plugins, theme, update PHP, reinstall WordPress, and nothing is working. Can some help me? I enabled debugging and this is the error I’m getting – it also causes an issue with losing connection and my site goes down.

Warning: An unexpected error occurred. Something may be wrong with www.remarpro.com or this server’s configuration. If you continue to have problems, please try the support forums. (WordPress could not establish a secure connection to www.remarpro.com. Please contact your server administrator.) in /home/xxxxxx/public_html/wp-includes/update.php on line 403

Warning: Cannot modify header information – headers already sent by (output started at /home/vandij6/public_html/wp-includes/update.php:403) in /home/xxxxxx/public_html/wp-admin/admin-header.php on line 9

The page I need help with: [log in to see the link]