This part starts with Don Juan reaching the bottom of the well and then untying himself from the rope. He walks a bit and opens a door, which leads to this large land with beautiful and sweet-smelling flowers.
While he's taking a stroll in this place, he happens upon a really good-looking house. He calls out to whoever's living inside (possibly to ask around or something) and a beautiful princess peeks out of it.
Don Juan is smitten, it's pretty much love at first sight. He and the princess, who is named Donya Juana, exchange pleasantries, and basically the prince tells her that he was indeed smitten and is very interested in her and he would like to court her, pretty much. And of course, as a bit of a test, she asks him to come inside the house so they could talk more.
Being the brave man that he is, Don Juan indeed goes inside, and the two get to know each other more through conversation. However, Donya Juana is also worried for the prince, since there's a nasty giant who acts as her guardian, and he doesn't exactly appreciate strangers and might kill Don Juan. The prince assures the princess that it's alright, and boldly says that the giant is nothing to him.
As they talk more, the aforementioned giant arrives at the house (probably went out on an errand of some sort) and notices that there's the scent of another person in the area, prompting him to call for Donya Juana (possibly to scold her or something like that). Don Juan, however, is the one who responds, saying that he's the one who insisted on visiting the princess.
Don Juan and the giant, after some more words between them, soon get into a fight to the death. And as you may expect, the prince is the one who won, slaying the giant in the process.
You'd think they would escape that place and go up the well by now, but Donya Juana hesitates. Apparently, she has a sister named Leonora, and leaving that place would mean leaving said sister behind. The younger princess in another residence, and is guarded by a serpent.
And of course, being the good guy that he is, Don Juan tells Donya Juana to stay put while he goes out to save Leonora.
Well, now we're getting to the romance bit, huh? With all the tropes and everything. But hey, we gotta give it to Don Juan, he makes the effort to woo Donya Juana.
By the way, if you read the poem, it doesn't really say much about the fight between Don Juan and the giant (if at all). It really just straight up describes how the prince challenges the giant, and then cuts to him winning, which I kind of find a little funny. For this, I'm glad I'm not mainly going with the textbook I have, cause that's a lot more verbose.
Really, if we could afford to not waste so many words, why not, right?
Other than that, I don't really have much to say about this part, but I do wonder how Don Pedro and Don Diego are faring up top. I mean, considering that there's nothing at the end of the rope now, who knows what they may be thinking?