This is the 12767th most frequent Polish word.
niewiarygodny
"Unbelievable" or "incredible."
Here, 'niewiarygodnie' modifies 'trudne,' emphasizing the exceptional difficulty of the task.
To było niewiarygodnie trudne zadanie.
It was an incredibly difficult task.
In this example, 'niewiarygodny' is used as an adjective to describe the view, meaning it was stunning to the point of being unreal.
Widok z góry był niewiarygodny.
The view from the mountain was unbelievable.
Here, 'niewiarygodna' characterizes the story as being difficult to believe, perhaps due to extraordinary or astonishing elements.