AFTER, IN, AFTERWARDS
AFTER is usually used as a preposition (followed by a noun):
I’ll do it after lunch.
Please call after 9:30.
AFTER followed by a time period is more often used to talk about past events:
After a few minutes he stopped.
IN followed by a time period is more often used to talk about future events:
He’ll be here in a few minutes.
AFTER can be used as an adverb, but only following another adverb such as soon, not long or shortly:
Tim came in at midnight, and Lucy not long after.
AFTERWARDS can be used instead, and can also be used as an adverb on its own:
His parents came shortly afterwards.
You can meet the actors afterwards. (NOT after)