Past Simple VS Past Perfect
1. Если уже один раз указали, что речь идёт о событиях, предшествующих другому действию в прошлом, то нет необходимости продолжать в Past Perfect:
We bought a new car last month. We had driven my parents’ old car for ages (и дальше уже речь продолжает идти о событиях, предшествующих покупке), but it started to fall apart (ИЛИ had started). We put a new engine in it (ИЛИ had put), but it didn’t solve the problems we were having.
2. Если последовательность событий ясна из контекста, то Past Perfect не обязателен:
The two leaders agreed to meet, even though the earlier talks had failed (ИЛИ failed) to reach an agreement.
“before, until, after” (последовательность событий понятна, поэтому можно использовать как Past Perfect, так и Past Simple):
The man arrived at the store before it had opened / before it opened.
He didn’t speak until he had heard / until he heard all the arguments.
After he had filled / after he filled his basket, he went for the checkout.
After Jimmy had finished reading / finished reading, he put off the light.