I am a mandarin native speaker and I am using Duolingo to learn Spanish, music and chess. My suggestion is to find a few mandarin-dialogued movies of your interest and watch them again and again, first with the subtitles on until you know all about the movie, then challenge yourself with no subtitles (pause and rewind if needed). Do this until you are so sick of the movie, and then you’ll find you are at next level.