"Bears do not know it."
Translation:Medvědi to nevědí!
Duolingo sentence database has its days sometimes... maybe the amount of people studying is too high for the database to keep up at certain times of the day. You're not the first with this issue, but it's only someone from Duolingo who can do something about it, not the contributors (they already complained about it). Make a screenshot if you want to help and speed up the process when they fix it.
And hopefully in the meantime it does not discourage you from learning! You're doing great! :-)