You have some great tips here already. I'll add one more that you could try:
Team up with an English writer. If you can find one who is trying to learn to write in your native tongue, even better! You can help each other. Correcting people's writing and vocabulary is usually seen as impolite. And often, as long as your meaning is understood, people won't say anything about how it's written or worded.
What will help you develop your English language is having someone who can critique your work. If you aren't made aware of the mistakes you may be making with your writing, how will you ever improve?
Reading, yes. But reading can be a very passive way of learning, particularly if you're reading at night, ready for sleep. Writing is a much more active way of learning but you need someone to correct it for you. You learn quickly from mistakes.
I did Arabic classes when I lived in the middle east and having a native speaker read my work really helped.
But try to find a creative writer, someone who knows the craft well, not a member of your family or a good friend who may be too careful of your feelings to give you brutally open and honest feedback on your work. I also find that readers who have no training or experience in the craft, often know something isn't quite right, but can't always articulate why it's not working the way it should.