Hello Iris. You start to improve your writing skills by writing things for others to see and correct. I put this in the comments, but I guess they don't show for answers.

Write as much as you can and have as many people read and correct it as you can. You will start to see 1) some new "native" ways to say things and 2) what typical grammar problems you have. Then you can focus just on those and not try to learn ever aspect of the language at one time. Keep track of these two things through memorization, sentence practice. For example, you can write a few sentences using a new structure and have people read those. Write sentences that are meaningful in your own life about your family, school, hobbies, career, etc. Another good practice is to rewrite your old writings and see how you can expand them by going into more detail. Try to apply some structures that you have been working on. Finally, read a lot! When you read you will notice certain structures and vocabulary that you might want to use in the future. Good luck!

Hello Iris. You start to improve your writing skills by writing things for others to see and correct.