From what I can tell the shortcode et_pb_sum is a Divi shortcode, but it is not a default one, it is not referenced in our configuration files for Divi and Divi-builder. hidden link hidden link
You can still follow the provided article and get it translated. If you find troubles let me know what you did and I'll do my best to help. I may also need access to a test server, or a Duplicator copy to troubleshoot locally.