after (preposition)- afterwards (adverb)

1. After is a preposition: it can be followed by a noun or an -ing form

• We ate in a restaurant after the film


• After seeing the film, we ate in a restaurant

1. After in not an adverb: we do not use it with the same meaning as afterwards, then or after that

• We went to the cinema and afterwards (then/ after that) we ate in a restaurant.
  (NOT... and after we ate in a restaurant)