Hello and welcome Nightshift.
As additional/alternative reference, you might like to also look at http://www.portforward.com/
I'm assuming that the problem is accessing the XAMPP server from outside the LAN. Therefore, I believe the router should run a 'virtual server' and send the network traffic to/from your XAMPP server. It can be very easy or frustrating.
Note: Saying '.. al ports are open, i also tryd with the firewall off .." seems a little contradictory. I raise this because having a fire wall, which normally blocks ports _itself_, somewhere forgotten or unknown can cause much heartache. In other words, be sure that _all_ firewalls are off between you,,, than asap, get them back on!