Chinese learn several hundreds, and sometimes thousands of Chengyus. They start to learn the Chengyus from an early age, in a similar way as we learn glossaries in the West.
If you tell a Chengyu to a Chinese person, they’ll know it most of the times. If you want to become completely fluent in Chinese, you should learn at least 300-500 Chengyus, they’re used everywhere, like in movies and newspapers.