我学汉语两年了。

Wǒ xué Hànyǔ liǎng nián le.

I've studied Mandarin for two years.

我今年十八岁。

Wǒ jīnnián shíbā suì.

I am 18 years old this year.

我很多年没见过你了。

Wǒ hěn duō nián méi jiànguo nǐ le.

I haven't seen you in many years.