Translation:This boy and this girl are a great couple.
Why suddenly "wspaniala" is "great" and not "wonderful" as in previous examples?
Does reporting actually ever help? I've usually had more response from the Forum.
para- here is couple, noun (feminine, singular, nominative) wspaniała is adjective infeminine, singular, nominative form.
A i B to wspaniała para (normal '"a", nominative case) = It is a great couple.
A i B są wspaniałą parą (letter "ą", instrumental case) = They ARE a great couple.
"chłopak" is an older boy, from let's say 13 (or less, it's very subjective) somewhere up to a young adult. It certainly makes more sense than "chłopiec" in the context of a couple.
I'd expect "chłopak" to apply from puberty until the age of ... responsibility (voting age?) - or longer, if he's someone's boyfriend.
Why boyfriend and girlfriend are wrong ? When I put my mouse on the polish words, they appear in the translation
Yes, but you can be "someone's boyfriend", not really "this boyfriend". If there is no possessive, then these words just mean "boy" and "girl".
Why "to" and not "sa"? You are referring to two people, not the couple itself.
I refer to Magics comment: Why don't you add the translation with "wonderful" as this word is "a good equivalent"?! I answered with wonderful as well and Duolingo says it's wrong :-(
The difference lies in the words "to" or "jest". If you use "to", it is Nominative (nouns and adjectives both ending -a in fem. sing). If you use "jest" it is Instrumental (ending nouns -ą, and adjectives -ą).
Example: X to Y = Zuza to piękna kobieta = Nominativ
X jest Y = Zuza jest piękną kobietą = Instrumental
But watch out, "To jest (add noun here)", (This is ...) will still be Nominative.
Not a native but fellow learner, hope this helps and if anything is wrong or misleading, pls correct.