I am travelling to Berlin and then going to Norway. Can I get a sim in Berlin which will be usable in Norway as well? Need majorly for data and GPS.
Yes, you can.
A recent EU regulation did away with roaming charges in the EU, which is what you may have heared before. But it's only half true. The EU roaming regulation covers all of the EAA (European Economic Area). This includes Norway, which is otherwise not a member of the EU. So if you buy any SIM card in Berlin, you will be able to use the roam like home option in Norway.
But there has also been a change in the registration rules for SIM cards. Until mid 2017 you were able to pretty much buy a SIM and register it under the name of Donald Duck under any existing address of a place you may have picked on Google Maps. Now you will need to present an ID document to have your card activated. As a result, prepaid SIM cards are available in less places than before and you may need to plan some time for the activation, though that should not be a big issue in Berlin.
Please also note that while on the cruise ship, your GSM device might switch to a satellite backed on-board maritime network. You can use that network for plain text messages and you will be able to make and receive calls, just at rates that are far from affordable.