Hello. I am an international student and I will take the SAT this year. But there is a difference between the math material in my country and the sat required math skills.
I really want a good score. Where and what problems should I solve besides those of the sample tests?
Please help 
Have you looked at any of the standard test prep books? Popular choices among students include Barrons, Princeton Review, and Kaplan. All of these offer great SAT preparation with review materials in all the subjects and practice tests. The College Board itself also releases a similar book. I suggest looking at these. A great studying technique is to simply take as many practice tests as you can. Since you’ve already noticed a difference in math material, I suggest not only solving many problems, but looking at the questions you missed, and keeping track of the particular area you have trouble with. This way, you know what information you have to review in order to improve your test score. The College Board site also offers free practice tests here: https://collegereadiness.collegeboard.org/sat/practice/full-length-practice-tests.