Banana Pi R1 Network Configuration Problem

When I connect the cable from the modem to the WAN port of my device, I can access the internet, but I cannot access the internet from another device through the LAN port. I’ve done switch configuration and interface configuration, but I’m not sure it’s correct. I can give IP to another device through LAN Port, but I cannot go to internet with that device. Can you share the configuration documents you are sure to work with? I’m currently running Ubuntu 18.04 and a touchscreen is connected to my device