When I came to England 4 years ago, I struggled with English language. Even though I could speak basic English, some phrases were unfamiliar and it has taken time for me to get used to use them correctly.
For example, the question "do you mind..?", which the form of asking permission was little bit tricky for me. Because I've been feeling funny to answer "No" to someone who asked me permission which I really didn't mind, I always answer "Yes!!" when I had to answer "No". The reason is "Yes" sounds positive and "No" sounds negative for me.
I've overcome this problem shortly and luckily I didn't upset anyone when I made a mistake!