Goeiendag, bonjour!
Did that already several times from Brussels.
Norway does not have a very extensive rail network, but it works quite well. Most mainlines between big cities only have 3-4 connections a day. Don’t forget that Norway has an insanely difficult geography and is sparsely populated. It’s absolutely not that frequent as in Belgium, only the region around Oslo has good local services comparable to what you’re used too.
The railway network in Norway like a star, and very centred toward Oslo. So avoiding Oslo, will be difficult if you take only trains :). All (normal) trains are included, for the regional trains you’ll need reservations.
Which you can get by calling EnTur (see below).
Sometimes busses are recommendend, to shorten your route. E.g. to get somewhere like from Ålesund to Bergen or Bergen to Stavanger. Going over Oslo for those, is time consuming. Whatever the options, you’ll get amazing views on the way. Buses are unofrtunately not included in the pass. But directly west from the North, you can only do by ship (Hurtigruten) or Plane (but then you’ll miss all the amazing landscapes);
For Norwegian trips, best plan here: https://entur.no/
There’s an interesting ferry connection to Norway to from Eemshaven (Nl), Hirsthals (DK) and Copenhagen (DK) should you want to return via a different option to Belgium.
