I recently restarted my Duolingo Korean course… I don’t really like it because they don’t explain anything - i have to learn using the practice questions. In the Mandarin course, there are tips and explanations before most of the practice tests, but there are hardly any in the Korean one.
Just as an experiment, I took the Checkpoint test(like a unit level test) without doing most of the practice topics and I still passed. I just had to rely on my ears and play the audio a few times… I could guess what the sentence meant.
Guess i have to look for some good grammar explaining sites… I’m currently using howtostudykorean.com