good email communication with HR One phone interview with analytical questions One on site interview with more analytical questions three people interviewed me and the third one was a manger who gave me really hard questions I could not answer on the spot

In my onsite interview, the first three interviewers are very nice, when come to the fourth people, I was told he/she was a director and the last interview was the most important one. However finally I was told that the director scheduled before was not available and some people else would instead him. When the forth people came, she just brought a phone and a charger, without pen, paper. She asked me to give her my resume and asked me who do I known in her company. Then gave me two brain teasers then continued to using phone.....