When do use "shilshom" and when do use "lifnei yomaim"? Last time I used shilshom (don't remember the sentence), it was marked wrong. Now I wrote lifnei yomaim hayinu beMesiba and it was wrong again
They have exactly the same meaning, you can use either. שלשום is shorter and more elegant perhaps, but לפני יומיים is also very much correct. The course is still in beta, that's probably the reason for the inconsistency.