How do you prepare for 2.5 hours phd interview?

Hi everyone, I recently gave a first round interview for a PhD position at University of Bonn, it was scheduled for 20 mins. After this, they sent me a coding task that involves 4 sub tasks and instructions for the 2nd round interview. I need to prepare a 20 minute presentation, speak with the lab members and the speak 1 on 1 with the project incharge. I am genuinely confused as to how to prepare for this. As far as my presentation is concerned, any questions related to that i think I will be able to answer but idk what else to prepare. The position is Causal ML and biomathematics. For context I barely have any experience with biomath, its a very statistics heavy position (I applied thinking its ML/coding based). Any tips would be really helpful! Thanks in advance!