Estructura del pasado perfecto?

Subject + had + past participle form of the main verb + before + subject + simple past tense .

. . .

Alex had completed the task before the teacher asked.

I had bought a phone before you came here.

Before + subject + simple past tense + subject + had + past participle form of the verb + .

. . .

Before I went to the office, I finished some business with her.

Before she went home, she had taken a test.

Subject + simple past tense + after + subject + had + past participle .

. . .

Mark ate after I had bought him a bat.

I went to the office after I had finished some business with her.

After + subject + had + past participle + subject + simple past tense .

. . .

After I had bought a phone, she came to the shop.

After she had gone, I came in.