First I had a phone interview with the HR Hiring Manager, a week later I had a phone interview with me would-be boss a week later they invited me to their Assessment Center (which consisted in an entire day at the HQ in Brussels, doing a problem simulation, then I had a case that I needed to solve and present in 4 hours, and finally another 1:1 interview with my would-be boss). Several managers were there for the presentations and interviews, they said they used to give an entire day for the case (to present early in the morning) but this time due to lack of time it was all done in one day, other than that it was not very hard but interpersonal skills were definitely what they were looking for.