I translated it as the sixteenth hour was very important how is this not a proper translation for the english?
really = opravdu, skutečně
very = hodně, velmi
May one use indeed here in place of really?
I added "was important indeed.". If you wanted other phrasing, please say it explicitly.
Could this sentence be also translated as "The sixteenth CLASS was really important"?
Lesson is accepted. Does class mean the same?
That's what I meant, actually. (I'm not such an expert in English, so "lesson" would do fine for me...) Thanks!
Class can definitely be used in the same way as lesson in UK English. "It was my fourth class of the day."
I wrote "The sixth hour..." (wrong, I know) but it was accepted as though I had only made a typo and corrected it to "The 1sixth hour..." (yes, with that number 1).
That is probably caused by the Duolingo automatic process that converts some numbers to words.