I had a terrible boss (russian) long long time ago, and he made fun of me (in front of others) the way I was saying: three, free and tree - it all sounded the s

I had a terrible boss (russian) long long time ago, and he made fun of me (in front of others) the way I was saying: three, free and tree - it all sounded the same (and still I have problems). I'm not a native speaker also (bulgarian). Nowadays I'm grateful to our son (~8 years old) who corrects us all the time, and it's kind of cool since this makes him feel good about it. I often would consult him when reading a book to him, how this and that is supposed to sound. He's even starting to correct my grammar, and learned early on about etymology (I had to geekimize him). Oh, that boss is long gone, he had another strange thing - correcting e-mails, people wrote to the point he wanted to correct one brit (and he was not the easy kind). I understand he also wanted to be helpful, but done privately would've been appreciated, done publicly - not so...