6 sentences

1. 费了老大劲，高低把这事办成了。

   fèi le lǎo​dà jìn, gāo​dī bǎ zhè shì bàn​chéng le.

   After a lot of effort, we finally managed to get it done.

   Source: Dong Chinese Dictionary

2. 听到这个消息，他心里老大不高兴。

   tīng​dào zhè​gè xiāo​xi, tā xīn​li lǎo​dà bù gāo​xìng.

   He was extremely unhappy when he heard the news.

   Source: Dong Chinese Dictionary

3. 他在家里排行老大，下面还有两个妹妹。

   tā zài jiā​lǐ pái​háng lǎo​dà, xià​miàn hái yǒu liǎng gè mèi​mei.

   He is the eldest child in the family and has two younger sisters.

   Source: Dong Chinese Dictionary

4. 他在家里排行老大，所以从小就非常有责任心。

   tā zài jiā​lǐ pái​háng lǎo​dà, suǒ​yǐ cóng xiǎo jiù fēi​cháng yǒu zé​rèn​xīn.

   He is the eldest child in his family, so he has been very responsible since he was young.

   Source: Dong Chinese Dictionary

5. 少壮不努力，老大徒伤悲。

   shào​zhuàng bù nǔ​lì, lǎo​dà tú shāng​bēi.

   If one does not work hard in youth, one will grieve in vain in old age.

   Source: Dong Chinese Dictionary

6. 他是我们公司的老大，所有大事都由他决定。

   tā shì wǒ​men gōng​sī de lǎo​dà, suǒ​yǒu dà​shì dōu yóu tā jué​dìng.

   He is the boss of our company; he makes all the major decisions.

   Source: Dong Chinese Dictionary