You could start writing the easiest topics again, but you might find this frustrating or boring. Perhaps you could try writing about topics that interest you - your favourite things? If you lack confidence in English essay writing you will only be able to write a limited amount at first. However, because you enjoy these topics you will always want to write more. If you keep writing more, your writing will increase in complexity and you will also feel comfortable writing about the things that are most important to you. I've not been in your situation, but I've seen a lot of people on italki improving their English quickly because they regularly challenge themselves to write about their hobbies and interests. This seems a more enjoyable way to practice than writing out basic, easy topics. Hope this helps. :)