Invention patents are generally difficult to search on a global scale.
Practical patents are relatively easy. As long as the structure of an article is improved and no one else has applied, you can apply for a patent.
Appearance patents are also easy, such as book cover design, the appearance of an article and so on.
You can apply for a practical patent for your improvement. You can ask the local patent office for details. They will give you a form, and you can introduce your project, improve it, and maybe attach CAD drawings. If the Patent Office thinks your article is practical, you can apply for a patent, and they will accept it, and then search in China. After passing, you can get the patent certificate in about one year.