The craze to learn English has always been in air. Do you want to know how to learn to write English and improve your spoken English? There is no silver bullet. By that, I mean that there’s no magical way of getting better at English. You can’t go from broken, ungrammatical English to perfectly fluent in two weeks.
You can’t. You can perhaps get better by 20-30% in two weeks.
If you’re already pretty good, then yes, two weeks is enough.
If you’re terrible, you need to spend months.
The first step to getting better at something is accurately recognizing your current capabilities, and understanding where you want to be.
English consists largely of grammar, vocabulary, pronunciation, and colloquialisms. These are in a specific order for a reason.
Grammar: This is the foundation of the language. If you have bad grammar, you’re always going to be weak at the language, no matter how many words you memorize, or how polished your accent is.
Sadly, nowadays schools no longer teach grammar the way they used to. Learning grammar without a teacher is hard. It’s not impossible though, especially in the age of the internet.
Assuming your grammar is reasonably decent, the next steps are much easier.
Vocabulary: You know how everyone tells you to read more? They’re right! Read as much as you can. The subject doesn’t matter so much, but do pick well written articles. It’s all on the internet. Read the Economist, read the New Yorker, the NY Times, the Hindu… Read it all.
When you read, make a note of the words you don’t comprehend. Look them up in a dictionary. You’ll also find that as you get better, you can often make a very good guess based on the context. And when you’re done reading, write. Try and use newer and more complex words to express your ideas.
Pronunciation: Easy! Watch TV and movies (English, naturally) and speak in English. Listen to people who speak well. Imitate how they speak. News anchors are a good place to start. But more than anything else, speak in English, and solicit feedback from people who know what they are talking about.
Colloquialisms: This one comes after everything else. They vary tremendously; American colloquialisms are totally unlike British ones, and Australian ones are even harder to figure out. It’s a cultural thing. Movies, TV shows, music, etc. This is something you pick up when you’re immersed in a culture, and people generally don’t mind that you don’t know about TV shows from the 80s & things like that. When you do pick up colloquialisms though, it’s MUCH easier to take part in social conversations.