"I am fine."
You're not saying "a fine/good" or "the fine/good", you're saying "is/am fine/good". - maika'i is being used as a verb in this sentence. Adjectives can be used as a verb and then include the "is" in the verb. You don't need to use equating sentences with adjectives in Hawaiian.
Here's a link to DL's audio files.
Here, in this Skill (Greetings). What is it that you feel you haven't been taught? The software should have introduced the word "maika'i" before giving you this sentence. It should have also introduced the word "au" before giving you this sentence. Unfortunately the Tips do not include an explanation that the grammatical subject follows the verb, but Duolingo is designed to teach through examples. It is expected that you might get many sentences wrong the first time you see them, but that after a few sentences you can start to pick up the pattern that the subject follows the verb and will be able to recognize that "Maika'i au" means, "I am fine."
Wolf wail? Wait, I work with wolves and "au" sounds Nothing like their howls. Often times, what we hear on TV is nothing like their calls. Here's a pronunciation link...for the word "au" not a wolf's howl: https://www.duolingo.com/dictionary/Hawaiian/au/efbfa919c7caeb86de98ad782057b280