I fail to understand when to use nominative and when to use instrumental with this verb. In sentences like this one and "Ten kot nie jest normalny" the nominative is preferred, whereas in sentences like "Jestem małym dzieckiem" and "Ten kot jest złym kotem" the instrumental case is used. What's the difference between those?
If you have an adjective on its own - it stays in Nominative.
If the adjective is in fact a part of a noun phrase - the whole noun phrase takes Instrumental.
Which audio gives the correct pronunciation? The audio which reads the entire sentence (splits the "e" and "a") or the audio for just "idalna" which combines the two?
The first one - any word with a dipthong that doesn't start or end in I/J is almost definitely a loanword.
Both "e" and "a" should be pronounced. I hear both sounds in the audio for the single word as well
The choice of whoever wrote this sentence was to write the default version from a woman's perspective. "idealny" would be what a man would say.
(The first Polish sentence that we put in the Incubator is the default one, it is the one that you get to translate. Then we put other versions, including "Nie jestem idealny" which is also a starred version just like this one.)