How to get from Tromsø to Bodø through Narvik with buses? How much does the trip cost and where to find the timetables?
The national travel guide for Norway is https://entur.no - literally "One trip".
It's available in English as well as Norwegian. It will show who operates the route, and possible changes. Not all different ticketing systems are integrated in the system yet. However, the two public operators are:
from where you can check prices.
It turns out there's one daily applicable departure, leaving Tromsø at 10:30, arriving 12hrs hours later in Bodø. It includes a one and half hour layover. It'll cost you 457,-