RD Gateway Change external port

Hi.
We are using RD Gateway 2019 to allow access to a group of office computers.
I was suggested that I should change the port to a different one, 4545 for example.
But I want the traffic to internal computers to use the default port of 3389.
Is this a viable option?
If so, how do I configure it on the server-side and on the external user side?

Thanks
Itamar