Hey,
I'm an experienced WordPress/Woocommerce developer, I can add the "I expressly agree, that before the revocation period has expired, you start with the execution of the contract. I am aware that with my agreement here, I will lose my right of revocation with the start of the contract execution." checkbox to the checkout page of your Woocommerce website. I will set it up so that a user cannot checkout without the checkbox being checked.
Kind Regards,
Anthony