4 sentences

1. 他们私下里非常亲密。

   tā​men sī​xià​lǐ fēi​cháng qīn​mì.

   They are very close in private.

   Source: CCMatrix

2. 私下里和他谈谈。

   sī​xià​lǐ hé tā tán​tan.

   Talk to him in private.

   Source: CCMatrix

3. 私下里和她谈谈。

   sī​xià​lǐ hé tā tán​tan.

   Talk to her in private.

   Source: CCMatrix

4. 有些学生私下里对我说，他们不敢在课堂上表达自己的观点。

   yǒu​xiē xué​sheng sī​xià​lǐ duì wǒ shuō, tā​men bù​gǎn zài kè​táng shang biǎo​dá zì​jǐ de guān​diǎn.

   Some students told me in private that they were afraid to express their views in class.

   Source: CCMatrix