English, no doubt, is the lingua franca: there are as many englishes with small E as there are communities and countries, old and new, across the world, even google can auto-write english. Truly lingua franca.
Only, you need to take English test in every two years to get your English checked; you need to watch tons of English movies from across the Anglophone world before you decide which accent you parrot; you need to keep on learning English from cradle to grave to prove first to your own people and then to others that you know enough synonyms of words like good, bad, and ugly so that you don't sound old-fashioned and judgemental; and before everything, you need to believe as you believe in sun and moon that English truly is the lingua franca -- it will help you speak in places where you'll never be invited to speak.
Rifat Mahbublives and works in London; in her memory she often lives in Dhaka, where she grew up, and in her writings, she lives everywhere. She writes both in Bangla and English. She wrote her PhD thesis on first-generation Bangladeshi educated women in Britain (2014, University of York).