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Your friend: Do you celebrate Halloween in Russia?

You: Yes, we do. And is it your favourite holiday?

Your friend: Yes, I like Halloween very much because it is a holiday for children.

You: What do you usually wear?

Your friend: We usually wear costumes of wiches and ghosts and go to the peoples houses, shouting (trick or treat!)

You: What was you wearing last Halloween? (я не совсем согласна с таким вопросом, но раз в ответе употреблено именно Past Continuous, нам остается подчиниться. А вообще я считаю, что здесь должен быть Past Simple, т.е. What did  you wear last Halloween? и ответ I wore a skeleton costume.)

Your friend: I was wearing a skeleton costume.

You: Did you tell ghost stories?

Your friend: Yes,we did. We were telling ghost stories and playing games all evening.