SLB Postdoctoral Research Associate interview questions

I had two phone interviews with two different people and then I was asked to come for an onsite interview/presentation. I didn't do a good job with my presentation. The people were really nice and I think it is a great place to work. I had some trouble understanding some of the people because many were international. One of the interviewers gave me a tough time and asked me questions I was not able to answer.