best way to see Norway & the fjords in 4 or 5 days

After you review the Norway in a Nutshell: Will you be coming from Oslo? If so I believe it is 4-5 hours to get to the fjords. On the way back though I believe the trip is much longer. It truly is an all day trip. If you do it in one day, you will be getting back to Oslo extremely late which I would not recommend for the seniors. We took the train on to Bergen for a couple of nights (lovely town) and then made the trip back to Oslo (7hrs). Its an exhausting day trying to do it all at once.

The Norway-in-a-Nutshell experience is designed to be done in one long day, though it could be be stretched by stopping half way and staying the night. The point of the Nutshell route though is to connect the two most important cities with one example of a classic Norweigian fjord.

So to better answer your question we need to know your in & out plans or preferences first. Do you need to go in & out of Oslo? Or can one leg be to/from Bergen?

The most simple and obvious choice for such a short time frame would be to spend 2 full days in Oslo, spend the 3rd day doing the Nutshell (it's a long day, but most of it is spent sitting and looking), then spend 2 full days in Bergen.

But there are more interesting fjord options if you had more time or didn't have any interest in the cities.

I assume you are visiting from some other destination in Europe, since it would be unusual to fly all that way for just 4-5 days. Where else are you visiting and what are your in & out options?