5 sentences

1. 两人聊得投机，不知时间已过半夜。

   liǎng rén liáo de tóu​jī, bù​zhī shí​jiān yǐ guò bàn​yè.

   The two were having such a good conversation that they didn't realize it was already past midnight.

   Source: Dong Chinese Dictionary

2. 由于性格相似，他们两人谈得很投机。

   yóu​yú xìng​gé xiāng​sì, tā​men liǎng rén tán de hěn tóu​jī.

   Because of their similar personalities, the two of them hit it off well.

   Source: Dong Chinese Dictionary

3. 老友重逢，大家聊得十分投机，他感到心情甚畅。

   lǎo​yǒu chóng​féng, dà​jiā liáo de shí​fēn tóu​jī, tā gǎn​dào xīn​qíng shèn chàng.

   Reunited with old friends, everyone chatted very congenially, and he felt very happy and relaxed.

   Source: Dong Chinese Dictionary

4. 股市在狂热的投机中不断攀升。

   gǔ​shì zài kuáng​rè de tóu​jī zhōng bù​duàn pān​shēng.

   The stock market kept climbing amidst feverish speculation.

   Source: Dong Chinese Dictionary

5. 这些商人企图通过投机倒把来牟取暴利。

   zhè​xiē shāng​rén qǐ​tú tōng​guò tóu​jī dǎo​bǎ lái móu​qǔ bào​lì.

   These merchants attempted to make huge profits through speculation and profiteering.

   Source: Dong Chinese Dictionary