Strato.de: TXT records
A TXT record is an entry within the Domain Name System (DNS) that provides supplemental information about your domain. You can create a TXT record that proves to Google that you own the domain.
Your domain provider doesn't support the TXT method of verification. Please select another verification method.
If you are unable to use the other methods because you don't maintain a website for your domain, please contact the G Suite support team, who will be able to assist you with an alternative method.