她看起来很年轻，完全看不出已经四十岁了。

Tā kàn qǐlái hěn niánqīng, wánquán kàn bù chū yǐjīng sìshí suì le.

She looks very young; you can't tell at all that she's already forty.

你还年轻，不要害怕犯错误。

Nǐ hái niánqīng, bùyào hàipà fàn cuòwù.

You're still young; don't be afraid of making mistakes.

他虽然年轻，但是做事非常有经验。

Tā suīrán niánqīng, dànshì zuòshì fēicháng yǒu jīngyàn.

Although he's young, he's very experienced in his work.