Thanks, but i am already study in mechanical enginnering. So which course i study part time? Whithout design course.

This will depend upon which area you wish to take up as a career. I think the best person who can advise you on this is your professor at your college. They can suggest other courses as they know what you are studying in college and which course can enhance that. Randomly it is tough to suggest any course like that. If you have any particula course in mind then let us know. We could help better like that. Another suggestion is to check the job portals for the career profile you have in mind and check what is required for that. Based on that research you could narrow down the other courses that will enhance your qualifications.