It depends on the vocabulary of the person and how dedicated he/she is (also on the age when did they start learning coz it wont be that difficult when you started at a young age) and tzuyu was frustrated coz she's not improving no matter how hard she practice during her trainee days according to her (twice tv 2015) I started learning korean at the age of 12 same as tzuyu. I used my skill somehow when i tried taking audition at JYP ent. 9 years ago but my korean now is rusty and regressed.
actually you could get that in many other video but here's what happened, tzuyu said 지겨워 (jigyeowo) which translated bored or tired instead of 즐거워 (jeulgowo) which translated have fun, which later she try to fix while everyone laughing. I know that this been answered I just want to add little detail why tzuyu make that mistake easily 😂
actually, i never see yeji sneezes (lol)... and for ryujin, i saw it once during their vlive.. hahaha.. here is the link of ryujin sneeze around 15:15... www.vlive.tv/video/165647?
