As a first option, you could spend your first months in Bergen in a student accomodation. However, they could not accept you since they prioritize younger students and families.
Anyway, if you consider this option this is the website to check. You need to ask the HVL HRs for help to contact with SIB to arrange it after they submitting the accommodation application to SiB, this way depending on the dates you may have more chances to get in.
Finn.no (translates to find) works like the classic ads page by categories, and you can buy (or rent) and sell everything: from houses, cars or appliances to clothing, boats or looking for a job.
There is a lot of movement in the website and it is convenient to check it periodically, for which I recommend to download their app, register and create search alerts to notify when there is a place that matches your requirements.
If you do not want to check it so often, you can also create a “home seeker” or tenant account for 499 kr for 60 days. In this way the owners will contact you directly if they match your requirements.
On the other hand, Hybel focuses only on housing. As in Finn, you can create a tenant profile but this time completely free (although you can do it premium and be more visible by 49 kr) that is active for a month.
In the case of Hybel there is no app, only with its web portal.
If you move within Norway
You will need to notify the moving to the Tax office, you can read more about it here.