Käännös - Italia-Englanti - amore tu sei tutta la mia splendida ...

"since you entered my life to become part of it" smth like this. That part is a bit unclear >> ...sei entrato a far parte della mia (vita).

"...since you began to be a part of mine (life),

There are some commas missing. Even if the original is faulty, they must appear in the translation.

"... part of it (my life)"

"since you began to be part of mine"

the use of the pronoum "me" is incorrect in the sentence... the concept passes but the form can be better...