1. Past perfect
Silviya Stoyanova

2. [had + past participle]
Formation
[had + past participle]
You had already bought a camera before you started the photography classes.
Had you already bought a camera before you started the photography classes?
You had not bought a camera before you started the photography classes.

3. Completed Action Before Something in the Past
I had never used such a nice camera before I bought the latest model.
I did not have any money because I had spent them all.
Katie knew the streets very well because she had been in the city a few times before.
Had you ever visited New York before the 9/11 attack?
Susan had never watched that movie before last night.

4. Duration Before Something in the Past (Non-Continuous Verbs)
By the time I opened the door, he had already left.
They felt bad about leaving their dog because they had lived with it for more than 10 years.
I had had this phone for 2 years before I bought a new one.

5. Specific Times with the Past Perfect
She had visited London once in 2005 before she started working there in 2011.

6. Use with before/after
She had visited London once in 2005 before she started working there in 2011.
She visited London once in 2005 before she started working there in 2011.

7. ADVERB PLACEMENT with always, only, never, ever, still, just, etc.
You had previously visited London before you started working there.
I had only met him when I realized I was falling in love.

8. ACTIVE / PASSIVE
George had repaired many cars before he received his mechanic's license. Active
Many cars had been repaired by George before he received his mechanic's license. Passive

9. Thank you !