Is handball a common noun

Yes, the Word handball is a common noun, a Word for any handball or game of handball.

For example: We played handball after school.

A proper noun is the name of a specific person, place, thing, or a title; for example:

• International Handball Federation (IHF), Basle, Switzerland
• United States Handball Association (USHA), Tucson, AZ
• Handball Lane, Indianapolis, IN
• "Fundamental Handball" by Bernath E. Phillips