The negation of a sentence (I eat <=> I don't eat) is something very easy to do in every language, but not in English. In English you need an auxiliary or modal verb to negate a sentence and if there is none, you have to add one. In Italian that' s very simple, you put a 'non' in front of the verb and finish.
Non mangio una pizza. I don't eat a pizza.
Non voglio mangiare una pizza. I don' t want to eat a pizza.
Non ho letto questo libro. I haven' t red this book.
Non ho comprato la macchina. I haven' t bought the car.