Do you mean the plants haven't set any fruit yet? If so, it is far too late anyway, especially in Norway. If the fruit are on the plant, a degree or so of frost won't harm them. Cut them and bring them into a frost free place where they can dry off and finish ripening ready for storage, or you could eat them straight away.
As you probably realise, the plants themselves will perish with even a degree of frost.

Hi Bertiefox! Thank you so much for your answer, I am so sad about my pumpkins and this awful cold degrees lately at night. After all the effort!! Well, we have about 11 beautiful pumpkins, they are still green, maybe 3 of them have a bit of beautiful orange, they are about the size of a tangerine and the biggest one is about the size of a melon.
The plant looks horribly dead, but the pumpkins are still there. I'm not sure what to do, some say I should just leave them longer. Like tonight is about +6℃ but two nights ago was about -2℃. What would you do??
My 5 year old son is so disappointed, he doesn't want green small pumpkins for Halloween :-))