When I try to remove a portal, I have to be in the portal area so it teleport me. I'm not able to remove my portal

Just found a way to do it, you have to stop the server, edit plugins/RedProtect/data/.yml and remove the line set-portal

You have two ways to do this without restart your server: https://github.com/FabioZumbi12/RedProtect/wiki/(08)-Portal-Creation#remove-the-portal