ningún is used before a singular masculine noun

ninguno is a pronoun, meaning “none”

ningunas are used with feminine plural nouns (e.g., ningunas razones)

Informal way of speaking - a nadie means “nobody.”

nada means “nothing”, not “nobody” - it is used with things, not people.

alguna is feminine singular

alguno is a pronoun, not an adjective - it is used to replace a noun

algún is used before a masculine singular noun

alguien means “someone / somebody” - it is used only for people, never for objects.