"One truth" is a literal English equivalent of the Italian phrase un vero. The pronunciation of the masculine singular phrase -- which also translates as "a truth" -- will be "oon VEY-ro" in Italian.
Ti farò diventare un vero uomo
Perché io voglio un amore vero senza te in Italian means "Because I want a true love without you" in English.
"A true Italian" is an English equivalent of the Italian phrase un vero italiano. The masculine singular phrase also may be translated into English as "one true (authentic, genuine, loyal, real, reliable, sincere) Italian." But regardless of meaning or use, the pronunciation will be "oon VEH-ro EE-ta-LYA-no" in Italian.
Un before a consonant in Italian means "a" or "one" in English.
Un bell'uomo in Italian means "a handsome man" in English.
Un attimo in Italian means "one moment" in English.
"A hallway" in English is un corridoio in Italian.
"In a relationship" in English is in un rapporto in Italian.
"An Italian policeman" in English means un carabiniere in Italian.
"An Italian mushroom" in English is un fungo italiano in Italian.
"I have a dream!" in English is Ho un sogno! in Italian.
"I am an accountant" in English is Sono un ragioniere in Italian.