I can't portforward minecraft server on my router?

Make sure that when you are port forwarding a port that you select the option labeled "Both" rather than selecting "UDP" or "TCP". You should also make sure that the correct IP address of your computer is in the "IP Address" box. If none of the above listed methods work for you, then try temporarily turning off your router's security, means that all ports are automatically forwarded.

Many routers do NOT do loopback (LAN2LAN via WAN IP). So even if you have port forwarding configured correctly, you might not be able to connect to your minecraft server using your public IP when you are on the same LAN. But make sure that it works when you connect to the LAN IP of the server. If that does not work, port forwarding is not going to work.

For the port forwarding you need to forward TCP port 25565 to the LAN IP of your server (assuming default minecraft port).

Then either have someone with a different internet connection see if they can connect to your minecraft server or go somewhere like http://www.canyouseeme.org/ and check port 25565 (or whatever port you set in server.properties and port forwarding, if you used a different port). Note that it is best to leave server-ip= blank in server.properties.