Bridged AP and switch

for the time being im traveling and staying with a buddy whom already has a router in place. i believe its a edge router lite if im not mistaken.
What im looking to do is take omnia with me and use it as JUST wifi acces point & switch behind his router that way i can connect my stuff via ethernet and wifi.

seen 1 post where i think Ondrej replied to a users post, though that was a couple years back.
how might i do this in LUCI GUI (not command line) . which settings to disable or enable.
i tested his advice here to ensure that i can get it to work (plug ethernet to wan on omnia and to an available lan port on other router, disabled dhcp, firewall)
though when i did this i only had 2 wireless devices successfully connect through wifi and others could not connect or they Would connect through wifi and say no internet connection.

also anything i plugged into ethernet on omnia was sort of slow in terms of speed

maybe this can help others who had similar questions. tnx in advance!

what i did was leave DHCP enabled and wala the devices that didn’t connect wirelessly before now connected . but why is this? i thought if a device was to be used as a access point only it would piggy back off the main routers dhcp? thus why it was recommended to disable DHCP and firewall on access point router.

any ideas?