Harry is nervous because it is the first time he will be meeting Fleur's parents. He wants to make a good impression but is worried how her parents will react to him.
Fleur side-alongs him to her family estate, a country house in the mountains near the Italian border, overlooking the Mediterranean sea, surrounded by a forest. He gets lost in the view, which is why he does not notice Fleur's parents and stumbles over his introduction.
With the good first impression failed in his mind, Harry tries a bit too hard to make up for that, which includes matching the Delacours with the wine.
Only, he has no experience with alcohol, which is why he ends up a bit too tipsy after the meal is over. So Fleur takes him up to her room and changes him into something comfortable to sleep in while teasing him about the evening.
Being drunk, Harry does not catch up on the humour and panics slightly, tries to apologise and, in far too many slightly slurred words, tells Fleur how much she means to him and why he tried so hard to make a good impression.
In the end Fleur manages to calm him down, kisses him gently and strokes his hair while he falls asleep with his head in her lap.