Ok real talk, I want to learn Mandarin, but as many have pointed out in the past, Duolingo sucks. What has worked for me in the past is Pimsleur. Are they still good? Looks like you can't get the CDs anymore and have to subscribe and get the app.
seconding Pleco, it has spaced repetition flashcards
Building Solidarity - One Word at a Time
Rules:
seconding Pleco, it has spaced repetition flashcards