Hi Manish!
You have made a good decision by choosing to write NDA. Approximately, 4 lakh applicants attempt this exam every year and only 6,300 of them are called for the interview round. Out of these people, only 320 cadets are accepted to the academy. Each semester, 70 for Air Force, 42 for Navy and 208 cadets for the Army are chosen. Now, you need to know that the NDA exam is conducted twice every year. The first exam is conducted in the month of April and this exam is called NDA-1, whereas, the second exam is conducted in the month of September and this exam is called NDA-2. They are named so only to prevent any misunderstandings. For the syllabus and all other information regarding this exam, you can refer to the following official link, which opens up a pdf:

Https://upsc.gov.in/sites/default/files/Notice-NDA-I-2019-Engl.pdf

The syllabus starts on page number 17. After referring to the pdf, if you still have any doubts, please feel free to comment.

Let me know if this answer was helpful and all the best for your future!