I don't have any interesting hobbies because I don't have enough time for one. My best hobby is surfing the net. To sound more like a native speaker, I'd say: something like: -I don't have any interesting hobbies because I don't have enough time for one. I'm best at surfing the web. -I don't have any interesting hobbies because I don't have enough time for one. The only hobby I'm good at is surfing the web. ("Net" is also correct in place of "web.")