Okay, I finished first year in high school in Korea. I didn't go through "go 3" thing, so I can be wrong. But since you want to know what other Korean pre-dent who went to high school in Korea, here I am.
I, too, thought you were joking when I first read your post. Obviously I'm wrong. anyway, I agree with other posters here. I don't know how hard the gen chem classes are at your school, but I would say these classes are demanding, timewise. I mean, I spent 2-3 hours a day just to study orgo almost everyday and was able to get A. (I don't even know how I did it but I just wanted to prove myself that I could do it.) That was just for orgo. Think about homework for other classes. It will be disaster to keep up with other classes.
Why don't you talk to other people in your school who have taken those classes and ask them what they think about your schedule?
Take it easy and enjoy your life!!😍