Past Perfect
Past perfect / past simple
Ex. 1
https://www.englisch-hilfen.de/en/exercises/tenses/past_perfect_simple_past.htm
Ex 2
https://www.ego4u.com/en/cram-up/grammar/simpas-pasper/exercises
Ex 3
http://www.adelescorner.org/grammar/past_perfect/past_perfect.html
Ex 4
http://englishgrammarexercise.com/past-perfect-mixed-exercise/
Ex 5 - yes / no questions
http://www.eflnet.com/grammar/yesnopastperf.php
https://www.grammarbank.com/present-perfect-or-past-perfect.html
https://www.grammarbank.com/perfect-tenses-mixed-exercise.html
https://www.englishgrammar.org/perfect-tenses-exercise-3/
https://www.englishpage.com/verbpage/verbs14.htm