Hi there.

Just keep solving questions until your concept becomes crystal clear and you develop a problem-solving approach. Just for the sake of your question, it is advisable to do 250+ different types of questions from each chapter. Cracking the NEET examination comes at the cost of hard work, patience, determination, continued practice, and a lot of focus on proper time management. 

The following books might prove helpful in your preparation. 

First of all, for all subjects i.e Physics, Chemistry, Biology study the NCERT books cover to cover at least twice. For Biology read NCERT as many times as possible. For only the text material of Biology, you actually don't need to refer to any other book. NCERT is more than enough for biology. You might doubt this but trust me NCERT is really really enough for Biology. I can't stress more on this FACT.

For Physics, after completing NCERT complete all examples and questions from DC Pandey Objective book of physics by Arihant publishers. Revise the material as much as possible. Before touching DC Pandey you can refer to HC Verma after completing NCERT.

You can also refer to online free learning platforms like Unacademy and Youtube. On YouTube check channels like Er Dushyant Kumar and Sachin Rana ( IIT B).

Hope this helps.