3 sentences

1. 唉，真可惜，我们还是输了。

   ài, zhēn kě​xī, wǒ​men hái​shi shū le.

   Sigh, what a shame; we still lost.

   Source: Dong Chinese Dictionary

2. 唉，我这就来。

   āi, wǒ zhè jiù lái.

   Alright, I'm coming.

   Source: Dong Chinese Dictionary

3. 他深深地唉了一口气，显得非常忧郁。

   tā shēn​shēn de āi le yī kǒu qì, xiǎn​de fēi​cháng yōu​yù.

   He let out a deep sigh and looked very depressed.

   Source: Dong Chinese Dictionary