How to use GPON in Bridge mode and OpenWrt router as main?

Installing and Using OpenWrt
1

Hi,

Total openwrt and networking noob here.

ISP provided Nokia G-2425G GPON router however I would like to use my Mi 3G (Openwrt) router as my main and use the ISP provided as just a gateway or in bridge mode.

I am totally lost here on how to configure this setting or what tutorial to follow.

Please help me guide in the right step.

2

That has nothing to do with OpenWrt. Ask your ISP and/or search for the admin guide for your ONT.
In most cases you will need to configure bridging [on the ONT] between ISP VLAN and one of the Ethernet ports.