4 sentences

1. 精通英语是困难的。

   jīng​tōng yīng​yǔ shì kùn​nan de.

   Mastering English is difficult.

   Source: Tatoeba

2. 她精通汉语，喜欢中国哲学。

   tā jīng​tōng hàn​yǔ, xǐ​huan zhōng​guó zhé​xué.

   She is proficient in Chinese, and likes Chinese philosophy.

   Source: CCMatrix

3. 我想我们凭直觉知道，实践并不等于精通。

   wǒ xiǎng wǒ​men píng zhí​jué zhī​dao, shí​jiàn bìng bù děng​yú jīng​tōng.

   I think we intuitively know that practice doesn’t equal mastery.

   Source: CCMatrix

4. 人们非常精通英语，所有的标志都是双语的。

   rén​men fēi​cháng jīng​tōng yīng​yǔ, suǒ​yǒu de biāo​zhì dōu shì shuāng​yǔ de.

   People are very proficient in English and all signs are bilingual.

   Source: CCMatrix