At first Introducing yourself and your experience then questions about basics and projects you worked on and the details of your role then online coding or calculation problems so on

After initial contact, I was interviewed by an engineer. The interview seemed very poorly planned, as the interviewer seemed unprepared and had no clue of what was being asked and what answers were correct. The interviewer confirmed that all went well and I should hear positive feedback. However, I received a rejection email from HR without any explanation of what went wrong. Overall, I had the impression that the company seemed unprepared/unorganized to the point where even the interviews seemed very poorly organized.