This is the 3411th most frequent Polish word.
wyzwanie
"Challenge."
"Wyzwaniem" is the instrumental singular form of "wyzwanie," describing the specific challenge.
Wyzwaniem w tej sytuacji jest skuteczne zarządzanie czasem.
The challenge in this situation is effective time management.
The word "wyzwanie" here is a noun meaning a challenge or difficult task.
To zadanie było prawdziwym wyzwaniem.
This task was a true challenge.
The word "wyzwaniom" is the dative plural of "wyzwanie," used here to indicate challenges presented to someone.