Réponse:
1-arrived-was writing
2-was crossing-saw
3-were they shouting-woke up
4-were fixing-opened
5-did mary break-was skating
6- was sleeping-knocked
7-saw-wasn't talking
8-was watching-went
9- didn't cross - stroke
10- didn't fall- was running
11- fell- was reading
12-was having- started
14- found- went-turned
15- walked-was talking-were working- were discussing
16- went - wasn't-was studying
17- was reading- was waiting
18- saw -wasnt
19-were driving- was texting
i hope it's clear, have a nice day !