It's so confusing with dier sounding like deer but deer is hert
Got it. Paid attention to my notes.... not "een kort staart".....!
Can you help me why use korte instead of kort?
Because "een staart" is a De-noun "de staart not het staart" and all de-nouns take an "e" when they have een before the work
They explain it here: https://www.duolingo.com/comment/3888221
On a scale of 1-10 for how complicated the rule is, I'd give it a 4. What makes it really difficult for learners is memorizing what words are common gender and what words are neuter.
If this is 4 then what is 10?