Unravel my writing struggle. How to learn English.

I’m trying to learn English so I write a lot. I write a lot and mistakes are made. I make mistakes because I’m still in the middle of a long-life learning process.
Putting all of my notes together in one file would be the greatest idea. I have to write something before I lose the flow. But there is a story behind how this started.
One day during an English lesson, I promised my teacher to write as frequently as possible to work on my language skills. At the beginning, I was quite a skeptic and even though I love writing in Polish I didn’t have an idea as to how I could even start writing in English. To encourage myself I started reading more and memorized the most interesting phrases. Then I rewrote them in several versions or even changed the word order for different meanings.
It’s quite easy to spot that each author has their specific way of expressing thoughts and favorite phrases.Not too long after the majority of the odd vocabularies will become familiar. Then I gave it a shot. It was a bit better but still not perfect. I felt like I was tilting at windmills and all went nowhere.
My dream – admittedly a bit unrealistic or perhaps unattainable – is to write a book in English one day. But Shush! For now, I’ll put it on the bucket list. Or on my list of unfulfilled dreams.