How long did it take for you to get used to formal and informal speech in Korea?

Hello! It's been about a year since I came to Korea. I am currently working in Itaewon, learning about Korean culture. At first, it was really difficult for me to distinguish between formal and informal speech levels. For a few months, I was really confused. But these days, I am gradually getting used to it. For example, when my friends call me '님' or '형', it feels different, and I feel more polite when speaking formally. How did you adapt at first? How long did it take for you to get used to formal and informal speech levels, as well as the various titles in Korea? And what was the most difficult part of that process? I tried reading books and talking a lot with friends, but it still doesn't feel natural. Do you have any tips or recommendations on how I can get used to it faster? I would really appreciate your help!