What can you contribute to our company?

I am an outstanding member at multitasking in a fast - moving office environment. At my previous company, working as a personal assistant, I managed 2 executives in the same time among the other tasks and office duties. I am flexible dealing with the variety of different tasks, as well as contributing my Customer Service skills. Having 3 years of experience in Customer service, dealing with different people from multiple countries every day made me confident that I can be a valuable team member in your company

To answer this kind of questions you need to understand what the interviewer really wants to know here.
The company before hiring wants to know how you could be useful, accomplished if you would be hired. For most positions other then entry - level jobs, the perfect employee brings his/her skills, experience, new ideas and qualifications, etc.
When during the interview you are asked about your contributions, they want to find out if you have the right skills for the job as well as your ability to to gain success in your new role.