If you want to write well in English, you need to understand what the parts of a sentence are, and how to use them. There are two basic kinds of clause: Dependent and Independent. With just these two types of clause, combined in different ways, we can write about anything and everything. That is, as long as we connect them in the right way.
It is important to know that there are a lot of ways to connect clauses, and you need to make sure you are choosing the option that says what you actually mean, not just something that you think sounds good(!).
Writing in a new language usually doesn’t come quickly, but with study and practice, it does come. Another great way to help your writing, by the way, is to spend as much time as you can reading. As a language teacher, I can tell you with absolute certainty that students who spend their free time reading become better writers sooner than those who do not.