There's a wide variety of different reliable and trustworthy books which can help you improve your English on such a deep level. Some of my friends used """Interchange "" and others used " Speak up ". Both of these books are really useful and can take your English to the next level. Best of luck

Yes there are lots of ways to learn English without taking courses. If you can afford it, teachers here are cheaper to hire than taking a full course. If you cannot then you need to find resources that work for you. You need speaking, listening, reading, and writing practice. You can get a lot of that here on italki, where you can post questions and discussion topics and post your writing as notebook entries that people can correct for you. In addition, you can buy or borrow books to read English and for English grammar. There are a wide variety of YouTube videos on English pronunciation and learning. There are also many free websites for learning English. And you can join various forums where people speak English to get a lot of practice writing. If you can’t afford a course you will just have to put the time in to find the resources you need. They are out there and there were a couple recent discussion topics that gave some good suggestions. Good luck.