Theme php error

Hello, I seem to having issues with being able to log in as well as make changes to my webpage. The website works fine and has no issues when navigating it, but when I try to logo into my wordpress account to update or add to a page I keep getting these error messages:

Warning: Invalid argument supplied for foreach() in /home1/mojocust/public_html/wp-content/themes/sydney/plugins/class-tgm-plugin-activation.php on line 2036

Warning: Cannot modify header information – headers already sent by (output started at /home1/mojocust/public_html/wp-content/themes/sydney/plugins/class-tgm-plugin-activation.php:2036) in /home1/mojocust/public_html/wp-includes/pluggable.php on line 1219

I have tried restoring the theme, but have had no luck fixing the problem. Can anyone help please?

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