Norway trip on July

I'm Thai and will go to Norway during 10-17 July. On 10-11 July, I have to go to Stavenger first as part of business trip, after that I will travel as backpacker. Anybody can suggest me, where shall I go? Actually, I want to go to Bergen, Trondheim and Tromso (want to go up north as far as I can). I will travel mostly by train but it can be flexible (if it's not too expensive). If anybody can recommend the place to go and how to, it should be very helpful for me.