Subject + 正好 + Verb
正好 means "just so happens," "coincidentally," or "exactly right." It indicates that something happened by fortunate coincidence or fits perfectly. For example, 你来得正好 means "You came at just the right time" and 我正好有两张票 means "I happen to have exactly two tickets."
我正好要去超市,帮你买吧。
wǒ zhènghǎo yào qù chāoshì, bāng nǐ mǎi ba.
I happen to be going to the supermarket; let me buy it for you.
这双鞋的大小正好合适。
zhè shuāng xié de dàxiǎo zhènghǎo héshì.
The size of these shoes fits just right.
他打电话来的时候,我正好在家。
tā dǎ diànhuà lái de shíhou, wǒ zhènghǎo zài jiā.
When he called, I happened to be at home.