I am having a problem where I can connect to my FTB Server with locahost and also with my internal ip address. However, my friends cannot connect with my external ip. I have watched numerous videos about how to port forward and how to set the server up, but my friends still cannot connect.
I don't know what you did exactly to activate port forwarding but my guess is that the description you used does not mention that some routers have an internal firewall too where you have to open the port aswell.
In addition to that, you might need to open the port in your local (PC) firewall too.
(This might also be the case if you use a VPN, like Hamachi which was already mentioned by Flaunting.)
Either follow the port forwarding route and make sure your router is properly port forwarding or the alternative is to use LogMeIn's Hamachi client which will create an artificial lan connection and your friends will be able to coonect to your internal IP.
The link to instructions for this are Here
Hamachi is free and i think pretty easy to use.