Because there are hundreds of different dialects in Norway, and we are only learning a written form of language. One would need to spend much time in Norway to understand the different dialects. Even people living in Norway can have difficulty understanding the Norwegian from someplace other than their home area.
*listens for the sound of new Norwegian learners' hearts breaking*
How is the plural formed? I think this is the first time I see a noun in plural here. Thanks.
have you looked at the information at https://www.duolingo.com/skill/nb/Plurals and https://www.duolingo.com/skill/nb/Definite-Plurals ?