We use no longer or not any longer to talk about the end of an action or state. No longer is more formal:
One day I could stand it no longer.
I couldn’t stand it any longer. I walked out and didn’t go back.
No longer often comes in the normal mid position for adverbs (between the subject and main verb, or after the modal verb or first auxiliary verb, or after be as a main verb), especially in more formal styles:
She no longer wears the dull colours of her former life and now dresses in bright, fashionable clothes.
In very formal styles, we can use no longer in front position, with the subject and verb inverted:
No longer does he dream of becoming famous. He knows his life will be very ordinary.
No longer or not any longer are the opposite of still.
She isn’t working here now.
She is working here now.
We use Not any longer as a response on its own. However, we don’t use No longer as a response on its own:
Are you still living in London?B:
Not any longer.
No longer. or No, not still.