"Hello, lovely gentleman" is an English equivalent of the Italian phrase Ciao, amabile gentiluomo.*
Specifically, the greeting ciao means "hi, hello," but can be used to start and end an interaction. The feminine/masculine adjective amabile means "lovely." The masculine noun gentiluomo means "gentleman."
The pronunciation is "tchow** ah-MAH-bee-leh DJEHN-tee-LWOH-moh."
*The term emphasizes how well-bred the gentleman is. But the phrase has the appeal of being the Nurse's description of Paris as "lovely gentleman" (amabile gentiluomo) in Act 3 Scene 5 of "Romeo and Juliet" by William Shakespeare (Baptized April 26, 1564 - April 23, 1616). So another possibility is signore, which also means "gentleman" and is pronounced "see-NYOH-reh."
"See you later, handsome boy" is an English equivalent of the Italian word Arrivederci, ragazzo carino.
Specifically, the infinitive arrivedere* means "to see again." The reflexive pronoun ci means "ourselves." The masculine noun ragazzo means "boy, boyfriend." The masculine adjective carino means "good-looking, handsome, kind, lovely, nice."
The pronunciation is "ahr-REE-veh-DEHR-tchee rah-GAHT-tsoh kah-REE-noh."
"Hello, Boyfriend" is an English equivalent of the Italian phrase Ciao, Ragazzo.
Specifically, the greeting ciao means "hi, hello." The masculine noun ragazzo means "boyfriend." The pronunciation is "tchow* rah-GAHTS-tsoh."
*The sound is similar to that in the English noun "chow."
"See you later, love! Kiss me!" is an English equivalent of the Italian phrase Arrivederci, amore. Bacime!
Specifically, the greeting arrivederci literally is "until we see each other again". The masculine noun amore means "love". The imperative baci means "(informal singular you) kiss!" The personal pronoun me translates the same in English and Italian.
The pronunciation will be "ahr-REE-veh-DEHR-tchee ah-MOH-rey BAH-tchee-mey" in Italian.