3 sentences

1. 这两个企业为了市场份额一直在暗中较劲。

   zhè liǎng gè qǐ​yè wèi le shì​chǎng fèn'é yī​zhí zài àn​zhōng jiào​jìn.

   These two companies have been secretly competing for market share.

   Source: Dong Chinese Dictionary

2. 为了搬动这块沉重的大石头，他浑身都在较劲。

   wèi​le bān​dòng zhè kuài chén​zhòng de dà shí​tou, tā hún​shēn dōu zài jiào​jìn.

   He was exerting all his strength to move the heavy rock.

   Source: Dong Chinese Dictionary

3. 我不知道他为什么总是跟我较劲，处处找我麻烦。

   wǒ bù zhī​dào tā wèi​shén​me zǒng​shì gēn wǒ jiào​jìn, chù​chù zhǎo wǒ má​fan.

   I don't know why he's always picking a fight with me and making things difficult for me.

   Source: Dong Chinese Dictionary