At the very bottom of the page in our Theme Frankfurt Product Demo, the following notice is included:

“This is a demo store for testing purposes — no orders shall be fulfilled.”

This option is not specific to Frankfurt, but comes from WooCommerce.

You can activate this notice in the back end via WooCommerce → Settings → General by simply adding a check mark for Store Notice.

Enabling the store notice
Enabling the store notice for the demo shop.

Store notice in the front end.
The demo shop store notice in the front end.