Hi
We may need some more info before we can answer the question fully.
Do you want to have the Layer 3 interfaces for the vlans on the firewall ?, is this what you mean by 5 vlans connect to one port.
if so how are your vlans spread out across the switches.
In essence you will need to connect all your switches to each other via trunks and then have the firewall interface connect to one of those switches on a trunk interface ans then create your logical interfaces on the firewall.
However this may not be what you want. Could you be a bit more specific.
Oh and what type of firewall is it ?
Jon