PAST SIMPLE VS PAST PERFECT .
Always remember that the Past Perfect is the "SUPERPAST" . Be sure you understand the difference between AFTER and BEFORE
https://www.ego4u.com/en/cram-up/grammar/simpas-pasper/exercises?ex04
http://www.englisch-hilfen.de/en/exercises/tenses/past_perfect_simple_past.htm
http://first-english.org/english_learning/english_tenses/comparison_tenses/40_simple_past_or_past_perfect_exercises.htm
https://www.ego4u.com/en/read-on/countries/usa/tour/orlando
https://www.ego4u.com/en/cram-up/grammar/simpas-pasper/exercises?ex05 ( watch out , they look like
independent sentences, but they are part of a story)
PRESENT PERFECT SIMPLE AND CONTINUOUS
https://www.perfect-english-grammar.com/present-perfect-present-perfect-continuous-1.html
PRESENT PERFECT AND SIMPLE PAST
https://www.perfect-english-grammar.com/past-simple-present-perfect-4.html
