I have reuploaded all folders, as well as installed wordpress on my localhost to see if reinstalling the entire site would help. Nothing changed.
When I copy the function code into wp-includes/template.php within 'if( ! function_exists('convert_to_screen') ) {} ' , it registers that the function exists, however it moves onto the error: class WP_Screen does not exist. I can keep hacking all these errors, but I feel like the issue is probably an easy fix, I just need to find the simple solution.