How fast can someone learn a language?

Related questions

1. Can adults learn a new language?
2. How effective is duolingo in learning a language?
3. Can you speak French after duolingo?
4. How does duolingo plus work?
5. How much money does duolingo make?
6. Does duolingo have a desktop app?
7. How does duolingo make money?
8. Can you actually learn a language in your sleep?
9. Which is better duolingo or Memrise?
10. Do you need Internet for duolingo?

Tags

1. #months
2. #three
3. #basic
4. #accounting
5. #learn
6. #hours
7. #fluency
8. #difficult
9. #should
10. #language
11. #twice
12. #languages
13. #equates