Yesterday I've started learning Chinese, and I've been using Duolingo only for now.
The most thing which I am irritating about Duolingo is that phonetic alphabets (Pinyin) are omited frequently in problems like quizzes.
I am not a genius so I cannot memorize a pronunciation of a term in one time.
So I am thinking changing the app or learning material(s).
For me, I want to be recommended some good grammar book or grammar website of Chinese.
BTW should I avoid using free materials of natural language learning rather than using stuff which was made with incentives?