My suggestion is to focus on your interview skills rather than language. You language can not be improved much in a couple weeks but your interview skills can. Treat interview as an exam and you need to prepare for it by researching what questions they may ask and coming up some good answers for these. After that, keep practicing these answers till the point that people can not tell that you just memorized these answers. Don't answer questions too quickly. Pausing for a few seconds before answering questions will not give the interviewer bad impression -- it will give you a little time to organize your thoughts.