Nǐ yīnɡɡāi qù lǐfà le.

你应该去理发了。

It's about time you had your hair cut.


Notes:

你(nǐ): you

应该(yīnɡɡāi): should

去(qù): to go

理发(lǐfà): have hair cut

了(le): particle word

Example:

A：你应该去理发了。

     Nǐ yīnɡɡāi qù lǐfà le.

     It's about time you had your hair cut.

B：好的。

     Hǎode.

     Sure.