Advise on IB subject selection

We are interested in talking in English to a current engineering student at TUM (Technical University of Munich) -- preferably mechanical engineering, or a recent graduate. We would like an hour of your time so that we can understand the process and your experience. My son tells us he is interested in studying engineering at TUM (Technical University of Munich). He is about to choose his IB subjects. We (his parents) can't support him very much as neither of us studied in Germany, and neither of us did the IB. He is also very young for his grade, which makes it more difficult for him in many ways. It is possible that there may be some ongoing work after the initial hour of conversation, which we would pay for separately.