It would be better if this were posted in http://www.italki.com/notebook There are a number of mistakes, and correcting it here would not be as easy or helpful.

To Whom It May Concern: I HAVE decided to take part IN the GG Program because I am NOT ONLY very interested in the food and beverage industry, BUT ALSO in the promotion of traditions. I think, IF I WANT to be a good candidate for your program, I have to work as an ITALIAN LANGUAGE teacher in AN international environment. I am A patient and diplomatic person. Discussion IS NOT a piece of cake for me SO I reflect before acting. I ALSO like sharing my knowledge with others AND learning from THEIR experiences. Besides, being in the company would be a great OPPORTUNITY for me to DEVELOP myself. Thank you very much.

I corrected it as I could, but please share this corrected version in notebook too. Native speakers can give you some other correction Dear reader, I HAVE decided to take part IN the GG Program because I am NOT ONLY very interested in the food&beverage industry, BUT ALSO in the promotion of traditions. I think, IF I WANT to be a good candidate for your program, I have to work as a ITALIAN LANGUAGE teacher in AN international environment. I am SO patience and diplomatic person. Discussions are not a piece of cake for me, AND I like to reflect before acting. I ALSO like sharing my knowledge with others, AND learning from THEIR experiences. Beside all, being in the company as could be a great occasion for me to improve and grow myself .