I wouldn't say you failed by any means. A Q of 50 means that you are obviously bright and logical. A V of 16 is "explanable" by someone who is not english-speaking. You have the tools -- do you have the time?
I don't know where you are at as far as you English goes, in addition to whatever you do I suggest reading American newspapers like the NY times or WSJ everyday, or the Economist
if you can get it. Reading passages of well written prose everyday
will give your "ear" a sense of the proper language.
Former Senior Instructor, Manhattan GMAT and VeritasPrep
Vice President, Midtown NYC Investment Bank, Structured Finance IT
MFE, Haas School of Business, UC Berkeley, Class of 2005
MBA, Anderson School of Management, UCLA, Class of 1993