The guy asked me about my background and then started asking some c++ questions. No were in the job description was mentioned about c++ as it was a ML position. I wasn't ready for a programming test at the first half an hour interview. He asked 3 questions and then he said I don't have any more questions, and I got immediately rejected.

first step: recruiter phone interview; if you pass, move to the 2nd step: hiring manager phone interview; if you pass, move to the 3rd step: onsite interview. the onsite interview is a group interview with a technical presentation.