1. Listen to English songs. For example, listen to Taylor Swift, One Direction (I don't really like them. But most teenagers like them) and Adele.
2. Read English newspaper like Star. You can use a dictionary if you can't understand some words.
3. Watch American/Australian tv series like Marvel's Agents of SHIELD or Once Upon A Time.
4. Watch English movies. Well, some movies have some nude scenes. So be careful with what movies you're gonna plan to watch. Watch Science Fiction like Inception or The Martian. They are really amazing.
5. Read novels. I'm not into novels but I've read some Science Fiction and Mystery novels. They are really great.
6. Talk in English to your friends or family members. Even though it's broken English, you could still improve yourself. Because pratice makes perfect!
^^ I hope these tips will help you. :)
By the way, try using Grammarly. It'll correct your mistakes so you can improve yourself. >> https://app.grammarly.com