Part XVII, article 343 of the Indian Constitution deals with the official language of Indian commonwealth. Bihar is the first state to adopt Hindi as its state language. Hindi is the 4th most spoken language of the world. It is spoken in many other parts of the world especially Europe, Africa and North America.
The second part of the question raises a very pertinent question as English has really considered as a global language and those who speak it are considered as trendy and smart. As it is quite evident that the Britishers ruled almost every part of the world and thus their imperialism led to the dissemination of English language as panoramatic level. The Industrial Revolution which was started in Europe and industries moved away from England taking English as its language thus this got special privilege among workers who work in that industry. Gradually English became a mass speaking language as it as the desired language which was a bridge to communicate between Britishers and the working community. It became a trend in India too who followed English as their working culture in the corporate world hence English speaking mass is given preference so that they could communicate the parts of the world too.
But we must respect our national language as it is mother tongue and gift of our ancestors.