She speaks French very fluently, but her pronunciation lets her down.

她法语讲得很流利，但美中不足的是发音不大好。

《牛津词典》

Our foreign teacher speaks Chinese very fluently as if he were Chinese.

我们的外籍老师汉语说得很流利，好像他是中国人一样。

youdao

I speak English very fluently.

我说英语很流利。

youdao

There's other disorders of language such as receptive aphasia where the person could speak very fluently but the words don't make any sense and they can't understand anybody else.

还有其他的语言障碍,诸如,接收性失语症,患有这种病的病人,语言流畅,但所讲话语没有任何意义,而他们也无法理解别人的话语

耶鲁公开课 - 心理学导论课程节选