I applied the working student position this April and had the interview in May. It was just a conversation which lasted for 45 mins. But I have to say in my interview there were lots of technical questions. But most of them were basic, like what is the difference between forward and future, what is the valur at risk, what is the topic of your bachlor thesis, etc. Interviewers were really nice. Actually the interviewers are not going to be the HR but the coworkers that you are going to work with. The whole process was quite relaxed.