At all means ‘in any way’. We use it with questions and negatives to add emphasis, but not with affirmative statements:
Do you want to swim in the sea at all?
She was not at all frightened.
We can use at all before or after an adjective:
Were you at all upset by Kevin’s behaviour?
They weren’t interested at all.
We often use at all at the end of a question to make the question sound more polite:
[ID is an abbreviation of ‘identification’]
Do you have any ID at all?
[a waiter in a restaurant]
Would you like any desserts at all?
We can use not at all as a polite response to questions asking Would you mind …? or Do you mind …? and as a polite follow-up response to thank you:
A:Would you mind taking this parcel to the main office?.
B:No, not at all.
A:Do you mind if I sit here?
B:Not at all.
A:That’s very kind of you, thank you.
B:Not at all.