I use Duolingo on and off to learn Japanese. Learning a language on Duo feels like playing a game at the beginning. When I started using it, my first thought was “this is easy and fun!” But as I started reaching new levels and as the topics started to get harder, I felt the need to use it more efficiently.
I repeat each individual lesson until it is totally completed without a mistake and write everything I learn on a notebook. Taking notes slows you down but in my experience it is the best way to remember the information you absorbed. Also if you pass to the next level without getting familiar with the new information, those bits of information accumulate and you start making a lot of mistakes. Then you feel discouraged and tend to drop it altogether.
In addition to repeating lessons and taking notes, I found other sources on internet to practice Kanji. I watch famous Japanese cartoon shows on Netflix with the LL google extension. This extension is a great help. It shows the subtitles in two languages and allows you to pause and check the words you don’t know the meaning of.
As I was expanding my sources day by day, I realized that Duolingo sessions turned into something similar to class experience. It is a traditional way of learning a language but a solid one. Every class comes with a textbook. And I’ve also recently found out that there is a site that brings together the language notes of Duolingo.I call it Duolingo Textbook. It is quite convenient cause grammar notes are scattered all around in Duolingo. It feels a lot clearer to have them all in one place. This is the link to all language pairs: https://duome.eu/tips/en
You can also download the Japanese Textbook directly from here: PDF