Why I can not improve my ACT score?

ACT is more of a race against the clock. If you're having trouble finishing problems then work on reading faster. Learn reading techniques like scanning an article, reading the question and going back to the section that it refers to. Look for key words and phrases. If you are having trouble with the content then take your time and comprehend what you are reading. For english you need to study grammar and vocabulary, which is just memorization. In science it is mostly reading graphs so read the question then look over the diagram for the answer. Don't try to look over the entire diagram before reading the question. For standardized tests in general just relax before the test and forget everything else in your life for those couple of hours. Eat some mints to help you concentrate. Get a good nights sleep before the test and don't study the night before. On the ACT guess on all the questions you have not answered yet since there is no penalty for wrong answers.