I am around of 500 to 520 marks in NEET abhyas 2020 app . for NEET,.. I want it to be 600+ ,is it possible within 20 days???

Actually, the mock tests are usually made a bit tougher compared to the actual exam paper as these tests are conducted to test the preparation level of candidates. Now if you are getting 500 to 520 in the mock tests then you can expect around 550 to 570 marks out of 720. You are on right track of preparation for Neet. Now to increase your score, you need to find out the weak areas that means the parts of topics which are not attempting or making mistakes. You have to find out those weak areas and work on them. Understand the concepts, study the part and give mock tests on those parts particularly. Now you have around 20 days left for Neet. After working on the weak areas, you must revise the entire syllabus for once at least. Keep giving mock tests and solve sample papers. The more you'll solve the more you'll score. You can also make short notes for the parts which you think difficult than others. Those short notes help a lot during revision and exam day. Write down all the formulae (Physics mainly) in a notebook so that whenever needed you can access them. Biology is the most important part and contains more marks so focus more on the chapters which carry more weightage such as Human Physiology, Cell, Genetics and Evolution etc.