Hallo @wahid.abassi 

Kan je eens in je browser naar 192.168.1.1 gaan en inloggen met admin en het Login Password dat achter de router staat. Als 2,4 GHz is uitgeschakeld bij de WiFi instellingen schakel deze dan weer in.

i can not go to this address

Do you have any WiFi extenders that your laptop may be connected to? if you do, try connecting your laptop to the router with a cable and see if that works. That way you can be sure you are connected to the router, and not to some WiFi extender that's lost it's connection to the router because of the WiFi issue. 

If you've never changed any settings in your router the easiest thing might be to just do a factory reset of the router. There should be a small pin hole button on the back side of the router that you can press with a paperclip or something like that. Just press that button for 10 seconds and let the router do it's thing for a few minutes, then see if connectivity is restored.