safari cannot find the server

Hi guys!!! So I've just upgraded my Mac with macOS Sierra but I made a mistake and I accidentally turned it off when it first restarted after the whole upgrade progress. So I didn't read or made any regulations for Siri or anything. Is that a problem ? Because the only thing I am getting since then is the message "Safari cannot find the server" when I am trying to surf on Safari while this doesn't happen with Chrome. Also AppStore connects and almost immediately disconnects... I've checked my Internet connection with another computer (and also I can surf on Chrome) and through network preferences and seems to be working fine.

Any help would be much appreciated!

Thank you