Woocommerce – remove related products error

Hi Guys, I followed the support request https://wordpress.org/support/topic/disable-remove-related-products-woocommerce-212?replies=10
edited the functions.php using wordpress….(it didn’t contain anything) so I added the code.
I received an error;
“remove_action( ‘woocommerce_after_single_product_summary’, ‘woocommerce_output_related_products’, 20);
Fatal error: Call to undefined function of_get_option() in /home/content/p3pnexwpnas05_data03/66/2595866/html/wp-content/themes/HeroPro/header.php on line 38″
I have since deleted the code and now receive this error;
“remove_action( ‘woocommerce_after_single_product_summary’, ‘woocommerce_output_related_products’, 20);
Warning: Cannot modify header information – headers already sent by (output started at /home/content/p3pnexwpnas05_data03/66/2595866/html/wp-content/themes/HeroPro/functions.php:1) in /home/content/p3pnexwpnas05_data03/66/2595866/html/wp-includes/pluggable.php on line 1196″
Now wheni go back to my products all I get is this error “
Fatal error: Call to undefined function of_get_option() in /home/content/p3pnexwpnas05_data03/66/2595866/html/wp-content/themes/HeroPro/header.php on line 38″

It was displaying my products before I entered and deleted the code, I just need to know how to get it back. Please
http://www.swiftekengineering.com.au/shop
Thankyou in advance.
PS I have paid for the hero pro theme but the support is almost non existent. I would really appreciate some help soon please 🙂