I'm confusing with uses of did not and were not/was not.. please explain

Did not - is used in simple past tense as a helping verb to frame a negative sentence when there is a verb in the given sentence. For ex:- He did not know anything about it. Was not - is used as a helping verb to frame a negative sentence with I,he,she,it,any name or singular subject in simple past tense when there is no verb in the given sentence. It's also used in past continuous tense as a helping verb. For ex:- She was not a student. Reeta was not coming. Were not - is used as a helping verb to frame a negative sentence with we,you,they or plural subject in simple past tense when there is no verb in the given sentence.It's also used like "were" as a helping verb in past continuous tense. For ex:- We were not poor farmers. You were not teaching well.

i ' m confusing with use of did not and was not /were not ...please explain