Check the other thread but you need a Z visa for internships. Double visas aren’t allowed in China and doubt if a Chinese company would pay you to study.
If in a full time program, you’ll be pretty busy as they are quite intensive. Mostly classes in the morning and some cultural activities in the afternoon. Not much time to study except at night.
Chinese university language programs on the mainland are quite rigorous. Chinese professors will teach you in the Chinese way and have no exposure to western learning so you mainly need to memorize everything that day and be prepared to use it the next. If you get mis-leveled, which often does happen when students pull out and there’s only a few students remaining, they shift you up or down.