Writing, I think, is generally more difficult than speaking. In every language, people learn to speak before writing. In speaking, all you basically need to do is to say what you’re thinking. It doesn’t have to be perfect as long as you can be understood.
In writing, it’s more difficult to express yourself because you can only use words. There are no actions or expressions or tone of voice. Grammar is also important in writing. I think in order to write better, you have to learn grammar first. Or at least make less grammatical mistakes.
Some of my students ask me how they can write better and my advice is if you made grammatical mistakes in your diary and I corrected them, remember these mistakes and avoid doing them in the future. I had a student before who did this. She never made the same mistakes so her writing kept better and better. Of course, she was also learning grammar in her school and I think that helped.
First, work on grammar. Be careful with your verbs, your infinitives and gerunds, conjunctions, and everything else. There are a lot to remember but when grammar isn’t a problem anymore you can explore writing more complicated things.