Once you have these plugins activated, you will easily see WPML integration on the top right corner of YayMail editor. From the language switcher, you can pick one and then the email editor will load the list of templates in that language.
Eg. (1) when I select "Deutsch", then (2) the list of email templates switch to German ones.
Please choose a template from the dropdown. Then you can go ahead and change the heading content.
You can add extra content specifically for German customers, like a custom image box and additional content.
The table titles can also be customized depending on your specific needs.
When you finish the translation and customization, you can enable the templates to put them in use. This means when a customer completes a purchase through the German checkout page, the German email templates will be sent.
While you're at it, be sure to check out other plugins to support German-speaking customers and other European legal rules: