HELP! New server trouble!

Alright from the top - i made a new server. But Now none of my friends cac connect. It always says Could Not Reach Server. I tried port forwarding and finnaly saw, that i used the wrong ip, since im supposed to use the external ip. So i tried that one but now when i use the external ip it says is a server already running on that port? and it's not, since this is my first server and definnetly the first on this ip. So please if there are any experts here that could help, please tell me what to do i REALLY REALLY wanna publish this server!
Tnx in advance