I'm 21 year old but no hair on my face. Any suggestions to help me growing facial hair?

You should ask your dad, brothers and grandfathers when their beards showed up.  Best if you wait this out as there is really nothing that can be done to accelerate your normal beard growth process as you get older.

You may still grow some more facial hair . You need to wait. A bit longer. This is a genetic condition if your hair still doesn't grow you can do facial hair transplant as it is very successful.