YOU SAID:

I don't know it's complicated to do that

INTO JAPANESE

それをするのが複雑なことは知りません

BACK INTO ENGLISH

I don't know how complicated it is to do

INTO JAPANESE

やり方がどれだけ複雑か分かりません

BACK INTO ENGLISH

I don't understand how complicated it is

INTO JAPANESE

どれだけ複雑なのか分かりません

BACK INTO ENGLISH

I don't understand how complicated it is