It would be a pity if you always had to agree. That's why
we have denying sentences. In English you normally add the
words "do not / does not" to make a denying sentence. In Spanish,
for instance, it's even easier, you just add "no"
before the verb.
In Norwegian this word is used:
You put it right after the subject and the verb:
Jeg bor i Norge. = I live in Norway.
Jeg bor ikke i Norge. = I do
not live in Norway.
Han snakker norsk. = He speaks Norwegian.
Han snakker ikke norsk. = He does
not speak Norwegian.
You do the same in questions, but
remember that the subject and the verb now have switched order:
de fra Norge? = Are they from Norway?
Er de ikke fra Norge? = Aren't
they from Norway?