Could you share some more information on how you set up spreed, if it’s the “Spreed video call” app or the “Spreed.ME” app with dedicated spreed server?
For both you don’t need to open specific ports, as the traffic is forwarded through the http/s ports.
In both cases: Most probably you need so set up a STUN or better TURN server to allow audio/video through your NAT. Here I am explaining how to do this, after step 7 it’s about the STUN/TURN server.