I always have a hard time to say yes or no.

There is a difference between Korean and English when replying yes or no. I'm always confused which is right reply. When my mom asks me "Wasn't the party fun?" and if I was fun, I say "No, It was fun." in Korea. But I have to say "Yes, it was." in English. I have been having confusion when I reply to negative sentences. If I have a question, I translate it into Korean and I judge I have to say yes or no. It always puts me in chaos. If I answer wrong, I hope you understand and fix it. I will try to be familiar with replying to negative sentences.