DynamicDNS

Many companies offer free dynamic DNS. But since I use DomainDiscount24, I also use their dynamic DNS service. To update the IP address of vpn.jeltsch.org, I need to send an https request to a specific URL, including a password and the hostname for which I want the update:
https://dynamicdns.key-systems.net/update.php?hostname=vpn.jeltsch.org&password=12345678&ip=auto