Here are my tips from one learner to another.
There are many ways to learn English. Let's focus on your question, which is about learning to write.
The best way to learn might vary from one learner to another. It mostly depends on the learner's background, immediate needs (proficiency tests, jobs, etc.), goals (how perfect they want to be, eventually), and his or her learning style.
In my opinion, the best way to learn English, given that your language is different from English much enough, is to learn to listen, to speak, to read, and to write, in that order. (Overlapping is possible.) However, more often than not, an ESL learner breaks this order, usually by learning to read and studying grammar first, before they can listen well enough. Not to mention their speaking skill. (And I was one of them.)
In your case, you can read well enough already. This is good. Now, there are two possible fastest approaches that I can think of, to improve your writing skill. The first approach is start writing now, and then check your writing against grammar rules, and possibly against the books you have read. This will improve your writing skill quickly, at first, but not by much in the long run.
Another approach, which I would like to suggest, but more challenging, is to learn to speak first. By learning to speak, I mean you make yourself speak spontaneously, the way native speakers do. If you have some native speakers who are willing to help you, this will be easy. If not, you still have TV, YouTube, movies, and so on, as your resources.
- This might be the opposite of what you want ("i want good writing then good speaking"), but I found that it's much more effective. (I changed my learning style about two years ago. Before then, I need to spend so much time just to write a short paragraph. Now I can write it as fast as my fingers allow, at about the same speed that I can type in my first language.)
It might start slow, but be persistent. Keep practicing. At least to the point that you can communicate confidently, if need be. You will notice that your vocabulary size will explode. To be able to communicate, you will need words, and you will observe those words you heard more intently. Soon enough, you will find that writing is not that difficult anymore. And if you want to improve your writing further, you can refine your writing skill by studying grammar later. (I'm doing exactly that now.) In my opinion, this approach is much better in the long run.
Hope this helps.