John Warrior wrote the workbook and answers the messages himself. There is no team behind this and no ticket system.
Email
henkjandekrijger@gmail.com — for questions before buying, refunds, a download that did not arrive, or a mistake you spotted in the book.
WhatsApp
Message John on WhatsApp
The chat opens with one line telling him which page you came from, so you do not have to explain the context first.