My native language is Estonian. I’m fluent in English. German is at a B1 level and Mandarin Chinese is at A2.1 level.
I have found the best language learning method to be immersion. And lots of it! That’s how I reached the level of fluency in English.
In high school I didn’t have to go to English classes because I had reached a level C1 in it (C1 was speaking, I would say that listening and reading were C2). After middle school my English was okay but definitely not fluent. Plus I struggled a lot with all the grammar rules. I didn’t go to high school right away and during those two years between schools I managed to reach that level. During that time I read many books in English and listened to English tv series a lot.
Did I learn any grammar rules? No!! I have forgotten everything I learned about grammar rules and I believe that when you go by the method of immersion then you don’t even need the grammar rules. If anyone said that I must make a sentence in past perfect, or something like that, then I wouldn’t be able to because when speaking I don’t think about the rules of grammar.
With German I initially used the site called lingq.com and found it useful. But I couldn’t be consistent with learning there. I started learning it in 2012. I often dropped it for months. Finally in August 2016 I decided to use the immersion method. I started with Harry Potter audiobooks that I found on Youtube. The listening was very difficult at first. By that time I had managed to learn about 3000 to 4000 words but while listening it seemed like I was hearing the language for the first time. It quickly started getting better though. I found some websites (bs.to and cine.to) where there are tons of German dubbed or German movies and TV Series. bs.to updates new episodes very quickly. The newest dubbed episode of Walking Dead was always available on the next day. Now in the end Of June 2017 I can comfortably listen to dubbed series and movies. Listening to the original German movies and series is a little bit more difficult. I haven’t been keeping track on how much listening I did from August 2016 to June 2017. I wasn’t consistent with that either so I think maybe 200-300 hours. I intend to keep listening German here and there but right now I’ve set my sight on other languages.
I have taken two different language courses in German. That was all a waste of money. I learned a few new words here and there but that was all.