You should start your preparation from  previous years papers  with this Understand the Exam Pattern and Syllabus then create your success plan according to your syllabus follow it regularly give mock test to know your strength and weakness.improve speed and accuracy and the most important thing stay motivated throughout the process.

With dedication, effective planning, and consistent effort, you can significantly improve your chances of cracking the NDA exam in 2-3 months. Stay disciplined, and don’t hesitate to seek help when needed. Good luck!