Moving internet from WWAN (wifi router) to WAN (LAN/ethernet)

I am sorry to post here. am a relative newbe and I am in desperate need for help.

I have connected my open wrt router to a wifi with a internet inorder to use it to check if it works with vpn. it create a WWAN and uses internet from this wifi. before that it was connected to another internet provider through the LAN not the wifi. now I wanna go back and switch it to the LAN (WAN) that was connected and was using before but I cannot I cannot even find its ip.

I am really lost here. I have to say that I am connecting remotely to the computer that connects to the openwrt.

I did it to help my old mom to bypass the heavy censorship in Iran so she can stream and watch shows but not the connection is lost.

is there a way to bring it back without having to reroot the whole open wrt? I have to say I am in germany and have no way to go back to her and she also doesnt have any body to help her. so I have to do everything remotely from here.

Can please some one help?