How to forward ports on 2 routers to the server?

Question

ASUS

Bundle:
Internet -> Wifi router ASUS RT-AC56U (paid static ip) -> WiFi router ASUS WL-520GU (access point) -> Windows Server 2016 server.
How to properly forward ports and connect to the installed crm (requiring a static address) with external ip?

Answer 1

Internet: the desired port RT-AC56U redirects from the Internet port to any port and WL-520GU IP you like. WL-520GU redirects from selected port to win2k16