How do you say

He’s in the middle of preparing for the GRE, with the hope of acing it in three months.

..in Chinese?

他正在准备GRE考试,希望三个月后能考好。

tā zhèng zài zhǔn bèi GRE kǎo shì , xī wàng sān gè yuè hòu néng kǎo hǎo 。

How do you say "He shed twenty pounds in three months in preparation for a marathon." in Chinese?