I also become comfortable in speaking/I become comfortably speaking too.

U speak korean very well

안녕하세요. 한국어를 4년동안 배웠어요. I come from China. I like to make diffident friends with diffident cultures. we can study korean together.

감사합니다~ you gave a really clear explanation ^^

sorry "It's okay if I speak casually/comfortably too, right?" and to clarify, usually this means, "It's okay if I use 반말(the informal form) too, right?"