This varies greatly from person to person. Factors like age, previous level of proficiency in the language, complexity of the language, and time spent every day in the lessons play a huge role in determining this. Some experts say that, on average, you'll need to study a language for anywhere between 500-1,000 hours to become fluent. If you wanted to do this within a year, you'd have to study the language 5 days a week, 2–4 hours a day.