Uw tips:Take a loot of food, count exactly how much is needed for all days and never buy anything there. Even supermarket food is expensive and not of the best quality. Restaurants are overpriced and often sell junk food as specialities. Also, book the cheapest possible accommodation and save whatever is possible. Oslo is a rip-off!
Oslo is an awesome city with a lot to offer. I spent the weekend there and was able to see most of the top attractions. But the city is rather too expensive for poor people of the European Union and its fallen currency. For a budget traveler who likes visiting museums and other venues of culture, the costs of such tours appeared unbearable, moreover in cold winter days.