Simple Past vs Past Perfect

The Past Perfect expresses the idea that something occurred before another action in the past.
The action that occurred FIRST (earlier in the past) is in the PAST PERFECT. The action that occurred SECOND (nearer the present) is in the SIMPLE PAST.

Before + simple past

After + past perfect

• We had had that car for ten years before it broke down.
• The car broke down after we had had it for ten years.