pełen niedowierzania in English:

A few incredulous spectators watched on as Paterson, ranked 23rd in the world, beat the champion.

his voice was incredulous

Many people were incredulous that such a small fire could have caused so much damage

What am I doing, she thought incredulously, thinking this way?

To judge by what he says, the answer is an incredulous no.

Miriam’s envious friends were incredulous about her engagement to a wealthy doctor