Your past work is one of the main criteria in the selection process
Briefly describe the projects you worked on and present one of them. That might be your bachelor thesis or a task that was a part of your job. Describe the problem, its importance, methods and outcome. Make your presentation appealing to a broad scientific/engineering audience, since the interviewers are of very diverse research interests (commonly in applied math, physics and computer science), yet detailed enough to evaluate your work. Emphasize your own contribution rather than the project in general. This part may take about 3-5 minutes.