How to configure ONT G-1425G-B in Bridge mode

Hi all, :grinning:
3 months ago our ISP provided us with a modem, formerly it was Alcatel, but now they are Nokia ONT G-1425G-B.
we cannot find the bridge mode explicitly in its configuration and we search in its technical manual and we do not find anything about the step by step of the bridge mode.
we look on the web but each one offers what it offers in the wan configuration page, this means there is no option to put it in bridge mode.
as it is previously Alcatel equipment, I would really like to have an answer on how to configure it clearly in bridge mode, what to do in the Lan page and what to do in the wan page?
I have a Sophos firewall, and I want to manage traffic from this firewall and avoid double NAT, is there a particular configuration on the wan port in PPPoE mode?
Thank you