backwards and forwards

in both directions alternately; to and fro

來(lái)來(lái)回回

he paced backwards and forwards nervously.

他緊張地來(lái)回踱步。

bend (或 fall 或 lean) over backwards

(informal)make every effort to achieve something, especially to be fair or helpful

(非正式)竭盡全力（尤指為實(shí)現(xiàn)公平或給予幫助）

we have bent over backwards to ensure a fair trial for the defendants.

我們竭盡全力保證對(duì)被告公平審判。

know something backwards

be entirely familiar with something

了如指掌