i been trying get my server public but my nepthew cant connect to it as i've done everything i can but no luck

Is this Hosted or from your own machine? Does he actually see the server listed?  If not, you can do this to find it.

If  you know  the IPS of the server & port you can have him hit F1 while in the loading screen and type client.connect <gamehost>  so it would look like this ...

client.connect 1*.*.*.*:28035