I am 20 years old and my height is 175cm . can i grow taller?

You're probably done: It's very unusual for a 20 year-old man to have any growth potential left unless there's a history of very delayed puberty. I think it's safe to say that if you're already shaving, then you're also done growing.

Sorry, you can't: Assuming you are a healthy 20 year old with normal development, the growth plates in your bones would have fused between 15 to 17 years and that means there is no more height gain after that...

You could check: Any further height would depend on having open growth centers in your long bones.A single x-ray of your wrist/hand can be examined for open growth centers. If they have closed, like they do for most males by 18, you are done.No meds/exercise/stretches/etc will help you grow taller if the growth centers are closed.