Canadian polyglot Steve Kaufmann says there is indeed a fast track to learning a new language. It involves doubling down on your listening and reading.
By taking the focus off grammar rules that are difficult to understand and even more difficult to remember, you can instead develop habits by greater exposure to the language. Kaufmann likens the learning process to a hockey stick.
In the beginning you make major progress as you climb the steep hill of the hockey stick, whereas the long shaft of the stick is the difficult part. Because you’re not seeing day-to-day changes, you might lose motivation. So, stay the course by consuming content that interests you.