The Fritz!Box is a very popular router which is mostly delivered by the internet provider. This router can be configured with our dyndns service.
More information about the router are available here -> wikipedia
Open the web interface of your Fritz!Box
Open "Internet" -> "Permit Access" -> "DynDNS"
As DynDNS Provider choose "User-defined"
As "Update URL" "https://myonlineportal.net/updateddns"
As "Domain name" your complete MyOnlinePortal domain