can not change theme options

Warning: Creating default object from empty value in /home/customer/www/rulek.rs/public_html/wp-content/themes/Avada/includes/lib/inc/redux/framework/FusionReduxCore/inc/class.fusionredux_filesystem.php on line 29

Warning: Cannot modify header information – headers already sent by (output started at /home/customer/www/rulek.rs/public_html/wp-content/themes/Avada/includes/lib/inc/redux/framework/FusionReduxCore/inc/class.fusionredux_filesystem.php:29) in /home/customer/www/sitename.rs/public_html/wp-admin/includes/misc.php on line 1431

Please help me fix this. I am beginner. Where to go to find this problem. I cant change the options everzthing iz freez