You need to be very serious and motivated and spend a long time every day practising,speaking to Native speakers,and listening to as much English as you can.

This depends on what you mean by fluent, but the best way to increase your level is to have a balanced approach that targets both receptive skills (reading, listening) and productive skills (speaking, writing). This engages your mind and body more completely than focusing on one thing. Even if your goal is to speak fluently, learning to write well can help you to understand word placement and can give you opportunity to thinking more fluently (we normally write more slowly than we speak, which allows us more time to think without it seeming awkward). If your English is already at a decent level, you are probably aware of the aspect that gives you the most trouble. (For me, it is listening.) You might need to focus on that aspect with a language partner or tutor. I would suggest talking to natives daily, as well.

Yes because you will get more fluent and you will hear them speaking correctly.Also if you surround yourself with English as much as possible (music,lectures,podcasts,movies) it will help you expand your vocabulary.But it will be hard in such a short period of time.You will need to spend a lot of time each day to succeed. Good luck!

http://www.businessinsider.com/how-to-learn-a-new-language-in-3-months-2014-10

 

Same guy, direct answer to your question!