想不起来

wǒ shí zài xiǎng bu qǐ lái tā de míng zi

我实在想不起来他的名字。

I am simply unable to call to mind his name.

wǒ zhēn de xiǎng bu qǐ lái le

我真的想不起来了。

My memory is really at fault.

yǒu shí xiǎng bu qǐ lái yuán gǎo zěn me xiě de wǒ jiù jí xìng fā huī gǎi biàn cuò cí

有时想不起来原稿怎么写的，我就即兴发挥，改变措辞。

Sometimes I improvise and change the words because I forget the original draft.