3 sentences

1. 他低着头咕了几句。

   tā dī zhe tóu gū le jǐ jù.

   He lowered his head and muttered a few words.

   Source: Dong Chinese Dictionary

2. 他一个人躲在角落里嘀咕，不知道在想什么。

   tā yī gè rén duǒ zài jiǎo​luò lǐ dí gū, bù zhī​dào zài xiǎng shén​me.

   He was muttering to himself in the corner, and I have no idea what he was thinking.

   Source: Dong Chinese Dictionary

3. 小鸽子咕的一声，从屋顶飞走了。

   xiǎo gē​zi gū de yī shēng, cóng wū​dǐng fēi zǒu le.

   The little pigeon cooed and flew away from the roof.

   Source: Dong Chinese Dictionary