The truth about this is simply, read or listen, a lot; and copy from your experience. Graded Reader Level 0 (and try to move up) or Satori Reader, should serve the purpose. Both of which also have parallel listening texts.
Recently, I found Hukumusume folktale collection from 🔉 🎙 Listen Every Day Challenge (Summer Edition) 🏖 - #136 by Zakarius which are short stories, and of course, not simplified just for adult learners.
- And collect vocabularies along the way.
Learning lots of vocabularies in advance helps too, to get into materials more easily, but be prepared to learn less relevant vocabularies (to your preferred consumption materials). Also, do learn usually Kana vocabularies and loan words.
- Vocabularies from WaniKani also helps, but it isn’t even hard to find seemingly important vocabularies outside WaniKani’s collection, even with WaniKani Kanji.
I recommend trying to remember vocabularies regardless of the Kanji, while of course knowing Kanji makes it easier. (Probably only concern with – the sentence or the context, is somehow too difficult.)
Nonetheless, I am still finding a way to learn grammar properly… In the end, I would probably still need to read grammar explanations in advance (from a structured textbook style).
- Explanations sometimes cover vocabulary and Kanji comparisons too, but not yet in structured style for now.
- In the past, I stepped from Tae Kim => Minna no Nihongo x4 => Tobira.