$#Pi$
1. David had gone home before we arrived
→ After David had gone home, we arrived
2. We had lunch then we took a look around the shops
→ Before we had lunch , we took a look around the shops
3. The light had gone out before we got out of the office
→ When we got out of the office, the light had gone out
4. After she had explained everything dearly, we started our work
→ By the time we started our work, she had explained everything dearly
5. My father had watered all the plants in the garden by the time my mother came home
→ Before my mother came home, my father had watered all the plants in the garden
