Assuming that this is your first trip to Norway you could spend at least two full days exploring Oslo. The Norway in a Nutshell combination train, boat bus tour from Oslo to Myrdal, Flam to fjord, Aurlandsfjord ferry, bus to Voss then train to Bergen can be a one or two day route. At least a full day in Bergen. That makes five days in Norway a squeeze. Fly from Bergen.
▲▲▲ Norway in a Nutshell A combination train, bus, and ferry trip to and through Norway's most spectacularly beautiful fjords — the Sognefjord and Nærøyfjord — passing pristine waterfalls, verdant forests, and take-your-breath-away scenery.
▲▲ Oslo Norway's sharp capital city, with its historic and walkable core, mural-lined City Hall, sculptures at Vigeland Park, and inspiring Nobel Peace Center, while the nearby Bygdøy district hosts museums dedicated to ships (Viking, Fram, and Kon-Tiki), the Holocaust, and traditional folk life. Holmenkollen Ski Museum and jump.
▲▲ Bergen Salty port town and medieval capital of Norway, with lively fish market, colorful Hanseatic quarter (Bryggen), and a funicular to the top of Mount Fløyen with great views.