It all depends on how much time you have to study. To learn a language quickly, you need to use it as much as you can in your daily life.
You need to use all kinds of skills such as listening to podcasts and watching English shows on YouTube. At first it might be difficult or boring, but keep trying and with time, things will improve. Another thing is to try writing a few paragraphs and post them on italki for others to correct for you. Also, you will need to read stories and news articles and try speaking as much as you can.
There is no secret method, you just need to do these things. Try not to focus on one thing, and make a plan of study tasks that you can follow.
Of course, if you need any help, feel free to ask.