The question whether our government should make an effort to preserve them by investing more money on that minority languages or not is still a debatable one
I think you should write: The question whether our government should make an effort to preserve minority languages by money investment is still a debatable one.
Last but not least, language is one of the essential factors creating the differences and unique cutures in the world
Do you mean the "differences between unique cultures" or "different unique cultures'?
Well, in general your essay is quite clear to me. But do you think it's a little long? Can you handle in 40 mins or less?
I see that you have long sentences, try to use more academic words to curtail those, thus make your essay more attractive I guess :) Your structures need to vary a bit to make your essay diverse :) That's my opinion :)