What is the best method to learn a language?
This is a difficult question, but if you reflect on the last 200 years of research, the following picture emerges.
You have a natural ability to learn any language at any age, but you cannot learn it like a child any more. You need to take it into your own hands and put systematic and conscious effort into it for at least 600 hours. This is one hour per day for two years.
Before you acquire a language and start using it intuitively and effortlessly, you must first learn it – move it from the short-term memory into the declarative memory. In order for that to happen, you have to learn and repeat things like words, rules or other facts.
Learning grammar rules doesn’t usually help with fluency. Grammar is best learned via induction. You are capable of discovering grammatical patterns through exposure to examples rather than being explicitly taught the rules upfront. As your brain stores chunks (rather than words), you should be memorizing these chunks (and not words), like collocations, phrases and sentences.
You memorize best if you space out your drills through time. Don’t cram a lot of material at once, but repeat regularly and systematically over time, preferably every day. Prioritize regular sleep and other healthy habits, like sport or diet. Mix different topics and skills, and change the conditions and places of learning. Use mental associations to help you remember things even better.
Listen a lot, even if you don’t understand the language yet. Include moving into your routine and listen when walking or exercising. Constantly challenge yourself by repeating, reading and listening to things that are above your current level. Prefer testing yourself actively with questions rather than just reviewing passively. It will be difficult for you, but it will bring the best results long-term. You have to think about the process and plan how to stay motivated. Set quality goals and be critical with yourself.
Language is social and cultural. You acquire language only by experience, by interacting with other people and making attempts to communicate with them. In communication you should prioritize understanding over accuracy. Embed language learning into your life. Actively seek opportunities to use it and prepare yourself accordingly beforehand. Have a tutor or a teacher that guides you and challenges you to express yourself in a foreign language.
Use a language app only as a companion, and synchronize it with all other activities. Be aware of your psychological barriers and false science.
If you do all of that, you will put yourself in a very good position to become fluent in any language.