"I was searching my files when I came across this photo."
Translation:Je cherchais dans mes dossiers quand je suis tombé sur cette photo.
Without the "dans", it would mean you were looking for your actual files, as opposed to you were looking IN your files for something. In other words,
- je cherchais mes dossiers = I was searching for my files
- je cherchais dans mes dossiers = I was searching my files
Is that a general rule, that after "quand", you need to use passé composé?
Not at all. "Quand" has nothing to do with it.
You have an ongoing action "I was searching" with no clear beginning or end. This is the perfect example of the usage of the French imparfait. It is then interrupted by a one-time action "I came across". This is expressed using the passé composé. This sentence construction is very popular among French language teachers to demonstrate the difference between imparfait and passé composé.
Notice how the verb tenses interchange going from one language to the other; I was searching (past continuous) becomes je cherchais (simple past) and I came across (simple past) becomes je suis tombé (past continuous). In french, in a same sentence, when two actions happen in the past, the first action is simple past, the second action, past continuous (passé composé).
I hate this question.
The sentence is too long so regardless of what you say, your answer will likely have too many things for the AI to complain about and it gives it too many excuses to falsely claim your answer was incorrect, when it was actually correct and should've been accepted.
I answered this comment several times through rewriting it in English as it told me to. Here're my answers...
• I was looking in my files when I came across this photo. - Incorrect
• I was looking in my folders when I came across that photo. - Incorrect
• I was searching my folders when I stumbled upon that photo. - Incorrect
This question is utter bµllsh¦t
I'm not trying to be rude, but this question is seriously annoying me >:(