Hey there,

I'm planning on doing an Interrail trip to Denmark and Norway in september. First to Copenhagen and take the ferry to Oslo after.

Now I wanted to take return trains to Bergen and back to Oslo and wanted to book some seat reservations for them. And while it's possible to do this through the interrail website (unfortunately not for the trains I want to take in sep cause they're not listed at the interrail reservations site, but according to vy.no they are indeed defenitely scheduled) I have a 1st class pass and I read I should make a reservation for a Pluss seat. But the interrail website only sells 2nd class seat reservations. So I figured I should make seat reservations by calling the Entur agency? But my question is how much will it cost to book a Pluss seat through this agency? And is there any way else to make a reservation? Online perhaps? 

I also read it's possible to book your seats at the station in Norway and for no extra cost even, but I don't know if the train I want will be fully booked at the time I will arrive in Oslo as there are only 3 days left before I want to take the train to Bergen. I arrive sep 24 in Oslo and wanna leave for Bergen on the 27th. Or are they usually still available 3 days in advance at the end of september? Don't really wanna risk it I guess or shouldn't I worry about it? Thx in advance for any answers!