Negations (negative sentence) always have "not" in a sentence.This means:
Verb to be: am not, is not, are not, was not or were not. (isn't, aren't, wasn't, weren't)
Verb to have: have not, has not, had got OR have not got, has not got, had not got. (haven't, hasn't, hadn't, haven't got hasn't got, hadn't got)
All other verbs + to do (do not, does not, did not OR doesn't, don't, didn't)
Auxiliary verbs (hulpwerkwoorden):
May not - remains the same!
Should not - shouldn't
Will not - won't
Must not - mustn't