"He is young and stupid."
Translation:Qup 'ej QIp.
Klingon doesn't have adjectives. Many English adjectives are represented by verbs in Klingon. These verbs can be used to make a sentence (like "the book is big") by placing the noun in the subject position (tIn paq). These verbs can also be used in a manner very similar to adjectives by placing them after the noun (paq tIn "the big book") and these noun phrases can then be used in a sentence (Doq paq tIn "the big book is red"). You cannot use either of the "and" conjunctions to combine verbs being used in this adjectival manner (David explains how to do that in his response).
However, if you are actually using the verbs as verbs, then you are correct that you would conjoin them with 'ej:
tIn paq 'ej Doq "The book is big and it is red."
Notice that in English we can easily shorten it to "The book is big and red." However, since these are verbs (and not adjectives) in Klingon, it is best to think of them each as separate full sentences being conjoined. So even if you saw the Klingon sentence tIn 'ej Doq paq, it would probably be OK to translate it as, "The book is big and red," but it more literally says, "It is big and the book is red."
No. Verbs acting as adjectives cannot be conjoined or strung together. If you need to modify a noun with multiple qualities, use conjoined relative clauses.
'IHbogh vIghro' 'ej qIjbogh the handsome black cat
tInbogh Duj, Qobbogh, 'ej peghbogh the big, dangerous, and secret ship
Doghbogh ghot 'ach Quchbogh the foolish but happy person
To an extent, you are right. This sentence could be translated as "He is young and stupid," or, "She is young and stupid," or, to keep it gender neutral, we could use the singular "they" and say, "they are young and stupid." But now we have a problem. The software can't tell if you mean singular "they" or plural "they". In a classroom, we could just check quickly which you meant, but the software is not designed to do that. While this Klingon sentence could be translated as any of the above three singular options (and also "it is young and stupid" too), it should not be read as having a plural subject and we want to make sure to reject plural subjects. For that reason, in this course, we do not accept "they" or "them" as a singular translation and only interpret it as a plural. That way we can make sure that users are clearly learning when the Klingon sentences are singular or plural or acceptable as both.
If you're talking about the pronunciation of the individual word token, that is unfortunately not the speaker, but Duolingo. The software doesn't distinguish between q and Q, so when it looks for the QIp token to play for you, it finds the qIp one and plays that instead. Amusingly, the actual QIp token (which you can't hear) has the biggest fluffiest Q ever, probably because it took me a while to figure out what was going on and I kept recording it more and more emphatically.
The sentence you can hear has the correct pronunciation.