Usages of rènzhēn
为了 提高 中文 水平， 我 每天 都 在 宿舍 认真 学习。wèile tígāo zhōngwén shuǐpíng, wǒ měitiān dōu zài sùshè rènzhēn xuéxí.
In order to improve my Chinese level, I study diligently in the dorm every day.
我们 在 图书馆 认真 复习 汉字。wǒmen zài túshūguǎn rènzhēn fùxí Hànzì.
We carefully review Chinese characters in the library.
Elon.io is an online learning platform
We have an entire course teaching Chinese grammar and vocabulary.