You are going to talk to your group members. You can come up with any topic(s) that sounds interesting to you. You are supposed to develop your topic(s) in the talk.
In the later part of the session, you are going to give a very short speech, say 30 seconds each. Every one of you has an equal opportunity to speak English in front of the people. Of course, You can use a note if you are not confident about your memory :-)