3 sentences

1. 他为了比赛每天苦练书法。

   tā wèi le bǐ​sài měi tiān kǔ​liàn shū​fǎ.

   He practices calligraphy hard every day for the competition.

   Source: Dong Chinese Dictionary

2. 为了练就这一手厨艺绝技，他苦练了整整十年。

   wèi​le liàn​jiù zhè yī​shǒu chú​yì jué​jì, tā kǔ​liàn le zhěng​zhěng shí nián.

   In order to master this culinary skill, he practiced hard for ten whole years.

   Source: Dong Chinese Dictionary

3. 冰冻三尺非一日之寒，他的成功离不开长期的苦练。

   bīng​dòng​sān​chǐ fēi yī rì zhī hán, tā de chéng​gōng lí​bu​kāi cháng​qī de kǔ​liàn.

   Rome wasn't built in a day; his success is inseparable from long-term hard practice.

   Source: Dong Chinese Dictionary