Seems like a very American itinerary, very rushed, and no time to properly visit any of the places you mentioned 😉.
2 full long travel days (with some night trains) get from Paris to Bergen by train (without visiting anything properly). Same for getting back to Prague, so that meas you’ll spend at least 5-6 days solely on transport of your two weeks. Some lovely views though, on the way, the Bergensbanen is really impressive.
Most straightforward route going will be: Paris-Cologne, Cologne-Hamburg, Hamburg-Kopenhagen (by day or night train). Kopenhagen - Göteborg, Göteborg-Oslo, Oslo-Bergen (possible by night train).
Or you take the night ferry Copenhagen-Oslo, also gaining some time.
Bergen is a good base to do hikes, you’re quickly in wild in unique nature in the immediate vincity of the city. Especially if you take some local busses. The hiking path from Fløyen to Ulriken (or the other way around) is recommendable, Gulfjellet,… easy acces to the biggest fjords, Nærøyfjorden (region around Flåm). Plenty of possibilities there. Voss, Geilo, all quite good bases (but smaller and not so interesting to visit, except to hike).
I’lld skip Amsterdam, go immediately furthest to Bergen, spend 3-5 days there, and travel futher. You can maybe take a Kystbus to Ålesund, from where you can continue to Åndalsnes, take the Raumabanen en Dovrebanen back to Oslo to a large part of Norway that way. Than visit Oslo (can be limited to one day, not that big), Stockholm (or anything in between for a more nature), Copenhagen and head back to Prague.
Use www.bahn.com to plan your trip in different stretches. Make sure to provide ample buffer time for important changes in Germany at least 1 or 2 hours, since German punctuality is very bad lately.
If you plan to take Eurostar (ex-thalys trains) from Paris to Amsterdam or Cologne, best reserve them asap.
A lot of crossborder trains into and out of Germany willhave mandatory reservation. Long distance trains in Sweden and Norway also have mandatory reservations. Get them on www.sj.se or www.entur.no respectively.
