The nights are necessary is the weirdest sentence I have ever heard. In what context would anyone say this?
Very good! I didn't think of that. Still, I think a sentence that needs such a specific context is less useful for a beginning learner of a language.
Would this mean "the nights are inevitable" or something else? Or it just makes no sense at all?
That's unfortunate to try to learn German and then the application takes points for not knowing English :(
It seems "nötig" is more close-to-life "necessary for someone". Besides, there is expression "etwas nötig haben" to express the idea "needs something". For example "Sie hat einen Stuhl nötig" ~ "She needs a chair". "Notwendig" is not used is such an expression and means a more generic "necessity". Just like in English you use "possible"/"impossible" without specifying, possible for WHOM and under what circumstances.
Could a native speaker of German clarify this?