There are many threads here about Norway. Ten days is a good time, but not a lot if you want both to see the fjords and the midnight sun (for which you have to go up to Bodų or even further north). Obviously you have to go in the period where the midnight sun is up. In Bodų June 3 to July 11, in Tromsų May 16 to July 25.

The easiest way would probably be to take the train to Bergen (perhaps with the Norway in a Nutshell (NIAN) opportunity). I'd stay two nights in both Oslo and Bergen, then take Hurtigruten to Tromsų (four days): You'll get to see some magnificents fjords, but still get to see the cities (Trondheim and Bodų in particular), and Lofoten. From Tromsų you can easily fly down to Oslo.