You can apply for a patent in the country where you live, the laws vary from one country to another as to term and requirements. A patent can be applied to any intellectual property if it meets the specifications of the local legal requirements. The only way to know for certain is to consult with a patent attorney where you live.

Most patent laws require you to make claims detailing the improvements you have made over other similar patented items. If you patent improvements over existing patented products or processes, the law may need existing patent holders whose work you claim improvements on to agree to grant you the right to improve on their patented work. As mentioned, the laws vary a lot from one country to another, so you can only get generalized information in a public forum.