Eat well is the literal English equivalent of 'Mangia bene'. A looser equivalent is 'Have a good meal' or 'Enjoy your food'. In the word by word translation, the imperative 'mangia' means '[you] eat'. The adverb 'bene' means 'well'.
You don't. Mangia bene is Italian. In English you say "eat well."
Così fan tutti! in Italian means "All men do it!" or "Thus do they all!" in English.
"Tutti".
Mi piace! Grazie a tutti! in Italian means "I like (it)! Thanks to everybody!" in English.
Mangia! Mangia! is an Italian equivalent of the English phrase "Eat! Eat!" The present imperative in question represents the form of the second person informal singular that is used with a family member, friend or peer. The pronunciation will be "MAN-dja MAN-dja" in Italian.
If you are told "Mangia" in an Italian restaurant, what are you being instructed to do?
"Thanks to all!" is an English equivalent of the Italian phrase Grazie a tutti! The courtesy, preposition, and masculine plural pronoun also translate into English as "Thank you to everybody (everyone, everything)!" The pronunciation will be "GRA-tsyey a TOOT-tee" in Italian.
"I miss you all!" in English is Manco tutti voi! in Italian.
"To everybody" and "to everything" are English equivalents of the Italian phrase a tutti. The preposition and masculine plural noun also translate into English as "to all" or "to everyone" according to context. The pronunciation will be "a TOOT-tee" in Italian.
"All sweets" is an English equivalent of the Italian phrase tutti dolci. The masculine plural adjective and noun also translate into English as "all candies," "all desserts," "all pleasures," and "all sweetnesses." The pronunciation will be "TOOT-tee DOL-tchee" in Italian.
mangia tanto (one people) mangiate tanto (more)
"Eat! Eat!" is a literal English equivalent of the Italian phrase Mangia! Mangia! The present imperative in the second person informal singular most correctly may be heard employed upon a listener who numbers among the speaker's close group of family, friends and peers even though it also may be used -- instead of the more correct, second person informal plural form Mangiate!([You all] eat!") -- with an intimate audience of more than one. The pronunciation will be "MAN-dja MAN-dja" in Italian.