Hello Aspirant, You can use HINGLISH (the mixture of Hindi & English). However, several SSB board nowadays do not entertain any other language except English. Thus, there is no escape

The best option is to try your best to speak in English . Show your effort at least. In cases where you feel you are stuck in a sentence, you may use Hindi until the point you are comfortable back on track again. If you are a good orator, it is definitely going to make an impact on officers and other aspirants as well. one must understand this that an Orator is not identified by the language, rather he is identified by the communication techniques he uses to influence others.