3 sentences

1. 他的演说听起来枯燥乏味。

   tā de yǎn​shuō tīng qi​lai kū​zào fá​wèi.

   His speech sounded dull and tedious.

   Source: Dong Chinese Dictionary

2. 他的发言语调平板，听起来很乏味。

   tā de fā​yán yǔ​diào píng​bǎn, tīng qi​lai hěn fá​wèi.

   His speech was delivered in a flat tone and sounded very dull.

   Source: Dong Chinese Dictionary

3. 单调乏味的生活让他的精神逐渐枯萎。

   dān​diào fá​wèi de shēng​huó ràng tā de jīng​shén zhú​jiàn kū​wěi.

   A monotonous life caused his spirit to gradually wither away.

   Source: Dong Chinese Dictionary