10 oraciones de simple past vs past perfect?

Simple past : I saw a movie yesterday.

I didn't see a play yesterday.

Last year, I traveled to Japan.

Last year, I didn't travel to Korea.

Did you have dinner last night?

She washed her car.

He didn't wash his car.

I didn’t know the answer.

She ate a hamburger.

I was in his house.

Past perfect : I had never seen such a beautiful beach before I went to Kauai.

I did not have any money because I had lost my wallet.

Tony knew Istanbul so well because he had visited the city several times.

Had Susan ever studied Thai before she moved to Thailand?

She only understood the movie because she had read the book.

Kristine had never been to an opera before last night.

We were not able to get a hotel room because we had not booked in advance.

A : Had you ever visited the U.

S. before your trip in 2006?

B : Yes, I had been to the U.

S. once before.