3 sentences

1. 还没到最后关头，我不甘心就这样失败。

   hái méi dào zuì​hòu guān​tóu, wǒ bù gān​xīn jiù zhè​yàng shī​bài.

   It's not over yet; I'm not resigned to failing like this.

   Source: Dong Chinese Dictionary

2. 他不甘心一辈子做一个无名小卒，所以一直非常努力。

   tā bù gān​xīn yī​bèi​zi zuò yī gè wú​míng​xiǎo​zú, suǒ​yǐ yī​zhí fēi​cháng nǔ​lì.

   He wasn't content with being a nobody all his life, so he worked very hard.

   Source: Dong Chinese Dictionary

3. 他甘心为了事业牺牲个人时间。

   tā gān​xīn wèi le shì​yè xī​shēng gè​rén shí​jiān.

   He is willing to sacrifice his personal time for his career.

   Source: Dong Chinese Dictionary