https://www.domaindiscount24.com/faq/en/txt-record
Please note It needs time for changes in the DNS to take effect. In case a single TXT record is longer than 255 characters you have to split it into two parts (like "1stpart" "2ndpart") to add it into a single line. This is because Strings in DNS records have a maximum of 255 characters according to RFC. By splitting the record with double quotes this limitation can be avoided.