People can keep their languages but English should be promoted as a universal language. It would be wonderful if all humans had a common language to speak, and English is best suited at this point.
There is no need to promote English. People all over the world are learning English because they want to.
English is a unique language. Only about 25 to 30% of words in English are “English”. English language "stole" 70% of its words from the languages the English people came in contact with.
There are many words from Indian languages which are part of English lexicon. For example: Bungalow: from Bengali word bangle. Cummerbund: from Hindi words kamar (कमर) for waist and bund (बन्द) for tying. Serendipity: from Sanskrit words swaran (स्वर्ण) for gold and dweep (द्वीप) for island. There is an interesting story behind this word. There is an island off Sri Lanka called Swarnadweep (स्वर्णद्वीप) meaning Golden Island When English landed on the island they were enchanted by its immense beauty. I don’t need to explain the mean of the word serendipity.
Most of the words related to government and diplomacy are of French origin – even the word government. The words ending with ‘tion’ are of French origin. School, sky, ski are Swedish words. Practically all scientific and medical terms are of Greek and Latin origin. There are many words of Arabic, Persian, Turkish and African origin.
We all know about the peculiarity of English pronounces and spelling. This applies to the words ‘stolen’ from the languages written in Hellenic, Latin and Cyrillic alphabets. The pronounciations are anglicized without changing the original spelling of the source languages. Thus we het the words which are pronounced the same but spelled differently. And spelled the same way but pronounced differently.