"I thought about you while watching this movie last night."
Translation:J'ai pensé à toi en regardant ce film hier soir.
"la nuit dernière" refused for "last night" ??????!!!!!!!!!???????? Well... someone can explain to me how to say "la nuit dernière" in english ????? Thanks a lot.
"Hier soir" means "last night", ie the night after yesterday.
"La nuit dernière" means "the night before", which is a bit ambiguous. It can mean the night before today, but it could mean the night before something else, even the night before yesterday. It would depend on context.
penser de is for opinions. penser à is for thinking about/of something
I believe this exercise is testing your knowledge of le gérondif usage and, as such, en regardant is all that is required to express "while watching".
I believe pendant is used for duration and generally means "during" whereas pendant que = "while" though I'm happy to be corrected by a native speaker. ☺