I have many times fp with other players, do i need too forward a port in my modem ( BBOX3 ) ??
I dont know wich port numer i have too use?

Starting networking diagnostics...

Your local network port (UDP) is 16000. All game traffic is routed through this port. This can be changed in "Settings" -> "NAT Traversal".

Attempting to connect to 3 test servers. This will take around a minute to complete...

Received data from 'server 2' through port 52572 (this is your WAN or router port)
Received data from 'server 1' through port 52571 (this is your WAN or router port)
Received data from 'server 3' through port 52573 (this is your WAN or router port)
14 seconds left.
9 seconds left.
4 seconds left.

Test Result: Symmetric NAT
Network Health: Poor
Recommended Action: Port forwarding recommended or switch routers. The only port you need to forward is UDP port 16000 on Voobly you do NOT need the direct play ports 2300-2400 and 47624.
Details: Your router assigned different public ports to all the test servers this will make it hard for users to directly connect to you. You will likely see a large number of fast proxies.

For help understanding this report or for more information go to http://www.voobly.com/pages/view/177#Network_Diagnostic_Tool.

You need to forward Port 16000 with the protocol UDP.

Related links:
https://support.voobly.com/display/vkb/KB1011+Ports+that+you+must+forward+to+play+or+to+host+a+multiplayer+game+on+Voobly
https://support.voobly.com/display/vkb/KB1013+Solve+Fast+Proxy+and+Connectivity+issues

Let me know how it goes!

I can only find a section portmapping in my modem, is this the same as portforwarding?
I must fill in two numers from : External start -- External End ?
You can see it in the attached file

The term varies depending on router model.

Add 16000 in the LAN port field and it's correctly configured.

Run the network diagnostics and share the outcome with me.
(Open a lobby > Options > Network Diagnostics)