1. If your's relationship is just average, you can simply answer: "I'm at work." Or "I'm working." This kind of answer is simple and clear, and it won't make people feel that you are too enthusiastic or too dependent.
2. If you want to show your professional image, you can answer "I am engaged in marketing in a company." Or "I'm an accountant." This kind of answer can make people better understand your professional background and skills.
If you want to show your personal interest, you can answer: "I like traveling, and I have just been to Yunnan recently." Or "I'm a music lover and I'm learning to play the piano recently." This kind of answer can make people better understand your personal hobbies and specialties.