3 sentences for 正经 (zhèng​jīng — serious)

1. 正经点儿，我们在谈正事呢。

   zhèng​jīng diǎn r, wǒ​men zài tán zhèng​shì ne.

   Be serious; we are talking about important business.

   Source: Dong Chinese Dictionary

2. 别在那儿胡闹了，我们在讨论正经事。

   bié zài nà​r hú​nào le, wǒ​men zài tǎo​lùn zhèng​jīng shì.

   Stop messing around; we are discussing serious matters.

   Source: Dong Chinese Dictionary

3. 那个孩子整天疯疯癫癫地跑来跑去，没个正经。

   nà​gè hái​zi zhěng​tiān fēng​feng​diān​diān de pǎo​lái​pǎo​qù, méi gè zhèng​jīng.

   That child runs around wildly all day, never being serious.

   Source: Dong Chinese Dictionary