You are correct.
However, I don't know who is teaching you to use words like "negro" or "negress," but those are offensive terms today. In the US we would refer to "African Americans" for either sex.
Also, feminine forms of many occupations are being phased out in common use. Equality between the sexes. We no longer prefer "waiter" or "waitress," replacing them with a neutral "server." Policemen are police officers.