this is our 1st language but English is becoming dominant as a global language.The other language may be important for thoir culture & values.English can be used as a language in any part of the world.It is like a universal language.
It is the language of science world-wide. English speaking countries have always been at the forefront of science and technology. Air-traffic control and pilots use English wherever and whatever country they fly from. But this doesn't answer the question. The disadvantages of the mother tongue are demonstrated when it is incorrectly used more often verbally. Our language is constantly evolving but certain grammatic rules are being broken along with those changes; 'I love it' is irritatingly being changed for 'I am loving it' because of fashionable idiosyncracies. 'How's yourself?' Is a question used instead of 'How are you?' Plain English is no longer used and the disadvantage of what is now considered the mother tongue has entered our lives.
Another disadvantage of the mother tongue is an obstinacy to learn another language which undoubtedly gets you better service in France and Germany. It is polite to learn a little and to use it, even badly, whenever the oportunity arises. Speak in French in paris and they will answer in English as is the same in Germany, regardless of competency. Speak English in New York and you are treated like a moron. ''Ill get a pastrami on rye" or "gimme a pastrami on rye" is magic but almost needs as much thought as any foreign language.