離開學校幾十年了, 能夠有機會利用網路再學習英文是上帝的恩典, 感謝Duolingo提供這麼好的網站及內容, 也佩服自己有那麼大的毅力, 能在半年內挑戰到25級. 雖然沒有更高的級數可以繼續, 我還是會持續練習, 避免退步. 再次感謝Duolingo!
Thank you for your valuable comments and if possible, please give me some information about other adequate sources.
Memrise, for one, is a great tool to increase or maintain your vocabulary. I've seen a lot of people recommend itaki to chat with native speakers. So I put it up there as well. I'd also suggest starting to read books in English. 读英文小说，用英文搜索youtube，google，在喜欢的领域逛英文论坛等等，包括duolingo。只要能使用英语都是宝贵的学习材料xD.
Another great way is to read entries you're interested in on https://en.wikipedia.org/wiki/Main_Page, which will direct you to more interesting articles or webpages in English.
Well, you can also try to contribute by translating between English and Chinese entries on wiki and even http://wikitravel.org/en/Main_Page (for your home town for example).
Please have fun!
Very good question! According to my experience, you will have already been familiar with the English grammar for our daily talking, but not enough for higher official examinations. Just for your reference, but it would be different to each individual.
As you said, if you are a new learner for English, I think you could repeat each session in the language tree until you feel better or you could come back again later.
But I still want to say that it is of great help for you to keep on learning every day. Without it, we are always fishing one day and drying the net for three days.