How long should I describe when asked to talk about my past research experiences by a potential PhD advisor during Skype interview? I have done two projects in the area of molecular biology. I have a Master's degree. So, I find that it requires more than 20 minutes to talk about them. My first-language is not English. I think this is too long, right? I would be tired, and the interviewer may also be tired. We may need additional time to discuss the research projects I did. So, should it be short? How many minutes are appropriate?
They ask about your research experience to learn more about your suitability for the position. They are not necessarily interested in the specific research results. If they are, they will look for publications after the interview or simply ask for more details.

Prepare a sales pitch with three main points: 


background/topic of the projects and also why you participated in them
main results and conclusions 
what did you learn from doing them (project management skills, exciting new technique, ...) 


You should be able to explain this in about 5 minutes. Be prepared to answer questions if they ask for more details.