Negative sentences in the past perfect tense express that an action or state had not been completed before another action or point in the past. To form negative past perfect tense sentences is very easy. All you have to do is put "not" after helping verb "had" (or with contraction "hadn't").
Regular Verb:
Affirmative: They had completed their homework before …
1. They / visit / museum / before it closed
2. I / learn / French / before moving to France
3. She / see / movie / before it was removed
4. He / complete / homework / by evening
5. He / know / the answer / before the teacher explained it
