>>34100Duolingo is too casual and generally unhelpful, LingoDeer does the same job better. If you want to get better at the language in general though, just go with Anki decks if you're poor or Wanikani + Bunpro if you got cash. Genki I -> Genki II / Minna no Nihongo -> Tobira for books. If you want to be able to converse, use HelloTalk.
