Hi again,
Scenario: At 1pm, I bought a sweater. At 2pm, I saw my friend, Tom.
1. I saw Tom. I bought a sweater. If you want to use 'tense' to make it clear that you bought the sweater first, say 'I had bought a sweater'.
2. After I had bought a sweater, I saw Tom. Yes. But the word 'after' is...