Bergen is a wonderful place to visit. We were just there last month, for four days, and these are the things we enjoyed:
-Walking the Vidden hike from Mount Ulriken to Mount Floyen: https://en.visitbergen.com/things-to-do/vidden-hike-from-ulriken-to-floyen-p984113
Going this direction, you take the cable car up, walk to where the funicular is (about 8 miles, lovely scenery), and take the funicular down. If you like nature I think you'd enjoy this.
-Norway in a Nutshell- the round trip itinerary from Bergen that involves a train to Voss, bus ride to Gudvangen, ferry thru the Naeroyfjord to Flam, and train back to Bergen via Myrdal. You may be doing some of this already if you are meeting up with people in Oslo. This is probably the most popular day trip from Bergen and it's totally worth it, especially the ferry ride, which is two hours.
-Hardangerfjord- we took the ferry from Bergen to Rosendal thru Hardangerfjord- just under two hours each way. Amazing scenery and Rosendal is a nice place to spend a few hours.
The fish market is right in the centre and is not very big. We had a very nice lunch in the part of the market in a building across the water from Bryggen. I don't remember seeing creamed herring but the seafood was excellent.
I hope this helps get you started but happy to answer any other questions about these activities. Good luck with your planning.
