Does this sound natural? I feel "when" doesn't go with "used to do something". It'd better be "I used to live in Korea, but back then, I wasn't used to using.."
gz154)When I used to live in Korea, I wasn't used to using chopsticks.
The first suggests that regardless of how long you lived there, you never got used to using chopsticks.
The second suggests that at some point during your time living there, you finally worked out how to use them.
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.