"Was" is the past simple of the verb "to be". It's not an auxiliary verb in this sentence.
I am young.
I was young.
I am not young.
I was not young.
I'm not sure what kind of question you want to form.
Were you at the party yesterday?
No. I was not at the party yesterday.
If you put a verb on its own at the start of a sentence (not a question), then it's an imperative.
Stand over there! (Imperative).
Student or Learner