Hello there. Considering the fact that you are interested in NDA, you can directly ask the questions here.

NDA is one of the most prestigious exam that take place for the candidates who want to join the Indian forces with a good rank from the start. The exam take place twice a year. Once during April and second nearly September-october. The examination is divided into two parts, the first one is completely based on mathematics and the main points is that if you are not able to qualify this exam, then your next exam will not even be checked so you need to perform in this exam. The second exam is general knowledge in which questions are related to physics chemistry English/Hindi general knowledge, history geography civics. If you are able to qualify this exam then you will be called for the SSB interview where all the further process will take place.

Hoping it might have cleared some of your doubts but if you still have any more doubts then please ask in the comments section of this thread.