Past perfect

We use the past perfect simple to talk about what happened before a point in the past. It looks back from a point in the past to further in the past.

Here are some links:

http://www.englishgrammarsecrets.com/pastperfect/exercise1.html

http://www.englishgrammarsecrets.com/pastperfect/exercise2.html

http://www.perfect-english-grammar.com/past-perfect-exercise-1.html

http://www.englishgrammarsecrets.com/pastperfect/exercise3.html

http://www.englishgrammarsecrets.com/pastperfect/exercise4.html

http://www.englishgrammarsecrets.com/pastperfect/exercise5.html

http://www.englishgrammarsecrets.com/pastperfect/exercise6.html

http://www.englisch-hilfen.de/en/exercises/tenses/past_perfect_simple_past.htm

http://www.ego4u.com/en/cram-up/grammar/past-perfect-simple/exercises

https://elt.oup.com/student/solutions/preint/grammar/grammar_09_012e?cc=global&selLanguage=en