Hit a brick wall. Need help! :(

You can use the self study tool addon to go over stuff repetitively to make sure you at least remember it now. You can also slow down if you need to, no shame in that. Duolingo is…bad to say the least. It really gives you no nuance on any grammar and oftentimes doesn’t accept answers that are actually correct (when typing especially). I would recommend bunpro in conjunction with reading through a textbook as well as Anki for actually useful vocabulary, as Wanikani doesn’t really give you the most useful stuff first.