3 sentences

1. 他到了青春期，已经渐渐懂了人事。

   tā dào le qīng​chūn​qī, yǐ​jīng jiàn​jiàn dǒng le rén​shì.

   Now that he has reached puberty, he is gradually becoming aware of the ways of the world.

   Source: Dong Chinese Dictionary

2. 对于处于青春期的孩子，家长应该多进行心理疏导。

   duì​yú chǔ​yú qīng​chūn​qī de hái​zi, jiā​zhǎng yīng​gāi duō jìn​xíng xīn​lǐ shū​dǎo.

   Parents should provide more psychological guidance for their adolescent children.

   Source: Dong Chinese Dictionary

3. 青少年在青春期往往会经历显著的生理和心理变化。

   qīng​shào​nián zài qīng​chūn​qī wǎng​wǎng huì jīng​lì xiǎn​zhù de shēng​lǐ hé xīn​lǐ biàn​huà.

   Adolescents often undergo significant physiological and psychological changes during puberty.

   Source: Dong Chinese Dictionary