> We walked 700km through Norway in the summer
“in the summer” must have helped. In the depth of winter, there’s less than 6 hours between sunrise and sunset in Oslo (https://www.timeanddate.com/sun/norway/oslo?month=12), just over 4 1/2 in Trondheim (https://www.timeanddate.com/sun/norway/trondheim?month=12).
To make matters worse, the sun doesn’t get high in the sky.