我wǒ不bù知zhī该gāi怎zěn么me办bàn。

I do not know what to do.

不bù知zhī不bù觉jué天tiān就jiù黑hēi了liǎo。

Before I knew it, it had gone dark.

他tā不bù知zhī发fā生shēng了liǎo什shén么me事shì。

He does not know what has happened.

不bù知zhī他tā何hé时shí回huí来lái。

I do not know when he will return.

我wǒ不bù知zhī这zhè件jiàn事shì。

I had no idea about this matter.