I would like to go to Oslo, Norway for 14 days during the Christmas season. Any suggestions on sight seeing, hotels, food, places to visit?
You can find Rick's Oslo highlights elsewhere on this website:
https://www.ricksteves.com/europe/norway/oslo Click on "At a Glance".
For a trip to Oslo of that length I'd want to use Rick's "Snapshot: Norway" guidebook (latest edition is from 2021) and at least one other, just to get input from more than one source. Be aware that the Munch Museum has relocated to the waterfront and is now simply called "MUNCH". The new, apparently very large, National Museum opens in June. Older guidebooks may have outdated information about those two sights. In addition, the Viking Ship Museum is closed and will remain so for several more years.
I don't know how pervasive it is in Oslo specifically, but in Scandinavia in general, hours of museums and other sights are often highly seasonal, with more limited hours and fewer open days each week outside of the peak summer season. I urge you to check the websites of the sights of interest to you for precise information. Guidebooks tend to assume travelers will be visiting at the time of year when the weather is best; hours in December/January might be very different.
What do you want to see and do? What are you interested in? Why have you chosen Norway?
I want to be there for the Christmas season. Along with museums, architecture, culture and food. I have only begun my search so I am open on where to go and what to see.
The Munch Museum has free admission on Wednesday evenings from 18:00 to close. You have to reserve your time slot on their web page. The web page states that you can reserve the free tickets for April-June, but it is now open for reservations for free tickets on Wednesday evenings through the end of 2022.
I want to be there for the Christmas season. Along with museums,
architecture, culture and food. I have only begun my search so I am
open on where to go and what to see.
That's not very helpful to be honest. Remember that there is limited daylight around Christmas so there will be limited oppurtunities to see the landscape. But apart from Oslo you should spend a few days in Bergen, make sure to take a daytime train between the cities to be able to see the views.