For example, if you major in electronic information, your graduation credit is generally 140. During your four-year study, the subjects you have learned can be roughly divided into: pedagogy subjects, compulsory education subjects, professional subjects, compulsory professional subjects, general professional subjects, and pedagogy courses. It is a course to cultivate college students' knowledge in an all-round way, including many fields, such as science, nature, sports and music. Specialized courses are your own specialized subjects. Most of the courses you choose in a semester are your own professional courses, and there are also general professional courses. You choose according to your own interests. For example, if you like art, you can take art courses at the Art University. . . You said that there will be students of architecture and civil engineering in your major course, which is normal, because they choose your department's course as a general major course to take credits.
There is also the question of making friends. If you have many professionals, it is difficult to make regular Korean friends. I quite agree with what you said upstairs. You should make at least one friend who can talk and say hello in each class, which is good for your study.
Studying in Korea, the mentality is the most important, and there are not a few international students suffering from depression. Studying abroad is very lonely and hard. You must overcome it and don't complain. Now that you have chosen, there is no need to regret it. I hope you can adapt as soon as possible and enjoy your life abroad.