I go to Star a game on Legions and every time someone joins they get a connection error! the Connection indicator says that i can host and join games but this still happens, please help!

Router?
Have you set UPnP on?

If you really want to host and cannot behind a router you can open a DMZ.
Be careful doing that.

I think its because I'm behind a router but i don't know about that stuff... YET

I'm taking classes

On the routers page - on your browser - enable Universal Plug N Play.
It is supposed to open the ports that games request automatically.