OPNsense with captive portal service

[moroms]

hello all,

need a help, I newly installed my opnsense and i want to configure it as part of my network, i already have a DHCP, a DNS and my firewall as gateway to the public, i am adding opnsense cause i want a captive portal so can users could connect to guest network with their credentials.

again, i don't want the opnsense to act as a DHCP or DNS or Gateway.
now do i still need three main ports for this to work? (LAN/WAN/Guest)
when the user is trying to connect to the guest network, the captive portal page is opening, also the authentication is working fine but after signing in, the internet is not working also, the captive portal is always on the log out page. checking the session page i found the user connected but without internet.

what could be the issue.

thank you.