How to deal with people

Hello 13yr old here. I have been atheist since I was 11 and everybody took it well my parents friends teachers.The don’t really care. Now there is a problem there is one friend that’s super annoying. Whenever I use term like “Oh My God” or “Jeez” “Go to hell” you get the point he is all like “I thought you were an atheist” ITS JUST A Term. What’s the worst he is Christian