1。 You have use what you have learned as often as possible。 If you don't use it, you will lose it very quickly。
And if you can't use what you have learned, then, you are not learning correctly。
2。
You have to work on the basics, like,
Can you speak simple sentences correctly?
Can you write simple sentences correctly?
Do you pronounce correctly?
3。
You have to learn by listening, this is really the best way to learn a language。 Learn by reading is also important, but not as natural and not as fast as listening。
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