PAST CONTINUOS PROGRESSIVE 

The continuous past is used for actions that were happening at a specific time in the past. As the present continuous, it is formed with the auxiliary verb "to be" and the verb + ing.

:) + WAS/WERE +V-ING
:) + WASN´T/ WEREN´T + V-ING
1. WAS/WERE + :) + V-ING + ?
2. WH + WAS/WERE + :) +  ?


here are several exercises to practice : https://www.curso-ingles.com/aprender/cursos/nivel-intermedio/verb-tenses-past/past-continuous