Past Continuous (Progressive) with WHILE and WHEN

PAST CONTINUOUS 

https://www.ego4u.com/en/cram-up/grammar/past-progressive/exercises

http://www.really-learn-english.com/past-progressive-exercises.html#01

https://www.englishclub.com/grammar/verb-tenses_past-continuous-quiz.htm

https://english.lingolia.com/en/grammar/tenses/past-progressive/exercises

SIMPLE PAST VS PAST CONTINUOUS 

https://learnenglish.britishcouncil.org/es/quick-grammar/past-continuous-and-past-simple

https://www.ecenglish.com/learnenglish/lessons/past-simple-vs-past-continuous

https://www.englisch-hilfen.de/en/exercises/tenses/simple_past_progressive.htm

https://test-english.com/grammar-points/a2/past-continuous-past-simple/

https://www.esl-lounge.com/student/grammar/2g50-past-simple-or-past-continuous-worksheet.php

https://www.englishexercises.org/makeagame/viewgame.asp?id=4889