2 sentences

1. 别自作聪明。

   bié zì​zuò​cōng​míng.

   Don't act smart.

   Source: OpenSubtitles

2. 他总是自作聪明，结果反而把事情弄糟了。

   tā zǒng​shì zì​zuò​cōng​míng, jié​guǒ fǎn'ér bǎ shì​qing nòng​zāo le.

   He always tries to be clever, but ends up making things worse.

   Source: Dong Chinese Dictionary