Hi, I've recently started learning Norwegian (Bokmal) and I'm wondering if other languages such as Swedish are relatively similar. If so, would they be worth learning?
they are extremely similar, and largely mutually intelligible. I would say that they are worth learning if you want to, or if you plan on living in one of those countries.
Norwegian and Danish are VERY similar. if you are level 10 in norwegian, you could probably test out of many skills in the danish course.
Swedish is less similar, but still recognizable
Although, something that makes norwegian different is that Norwegian has 3 genders, while swedish and danish only have two! (at least as far as I know in modern swedish and danish)
Et- neuter, En- masculine, Ei- Feminine
That's true but it's not far-fetched to say that the feminine gender is almost only a stylistic matter. In practice, neglecting it can't be considered an error asaik (although some teachers I have spoken to believe this may change, soon). I'm happy with the Norwegian feminine compared to Swedish declensions of nouns. The common gender ones have 4 regular patterns (Norwegian basically has one, the words that go like "en sko, skoen, sko, skoene" are really few) and the neuter ones have two (one with plurals in EN which can be easily mistaken for singular definite common gender nouns)... Not sure about Danish.
Norwegian is essentially a language written by a Dane and spoken by a Swede. Some of the aspects of Norwegian are more Swedish (e.g. double definite for adjectives before definite nouns), most spellings and special characters are a bit more Danish.
However, you are likely to have a much easier time understanding spoken Swedish than spoken Danish. People with an interest in Scandinavian languages coming to university are often advised to make Danish their main language because it's the hardest and will make understanding spoken Norwegian or Swedish easier.