Comparing “yǐhòu” and “de shíhou”

吃完饭以后我们去散步。

Chī wán fàn yǐhòu wǒmen qù sànbù.

After eating, we will go for a walk.

吃饭的时候不要看手机。

Chīfàn de shíhou búyào kàn shǒujī.

Do not look at your phone while eating.

他来中国以后进步很快。 / 我认识他的时候，他还不会说汉语。

Tā lái Zhōngguó yǐhòu jìnbù hěn kuài. / Wǒ rènshi tā de shíhou, tā hái bú huì shuō Hànyǔ.

After he came to China, he improved quickly. / When I met him, he still could not speak Chinese.