"Quietly watching" can be translated as "安静地看着" in Chinese.

The phrase "quietly watching" is formed by combining the adverb "quietly," which means "in a quiet manner," with the verb "watching," which means "observing something or someone attentively."

Here are some example sentences in Engpsh and their translations in Chinese:

She sat quietly watching the sunset. (她安静地坐着看着日落。)
He stood quietly watching the birds in the tree. (他站着安静地看着树上的鸟。)
They watched quietly as the play unfolded. (他们安静地看着戏剧展开。)

I hope this helps!