Koreans in China have more opportunities to contact Korean in their daily life, because their living area is close to the Korean peninsula and they have close economic, cultural and personnel exchanges with South Korea. Korean TV dramas, music and variety shows are also very popular in China, so Koreans in China have relatively more contact and understanding of Korean.
However, the degree to which Koreans in China can understand Korean varies from person to person. Some Korean young people in China can understand some simple Korean, but they still can't understand some rare words and special usages in Korean. For some older Koreans in China, due to historical and cultural factors, their acceptance of Korean is low.
Korean and Korean are basically the same, but there are differences in intonation. There are many foreign words transliterated directly in English in Korean, and Chinese and Japanese are mixed in Korean. Some young Koreans can understand foreign words in Korean because they often watch the Korean drama Han Zong. Those who have studied English should be able to hear them. So Koreans can speak pure Korean as long as they pay a little attention to their intonation.
Generally speaking, Koreans in China can basically understand Korean, but the specific degree of understanding varies from person to person.