Hello! Just relax! It is so easy to think too hard about things and get all panicked for no reason. Honestly, just say whatever comes out naturally... maybe something like, "Hi, I'm Najoi" (if that is your name), followed by a couple of sentences about whatever it is you are supposed to be talking about. If it literally is about "you", then you could make a cool slide with some pictures and/or a word cloud that matches some of the things you are going to say... your interests, why you are at the Summer School, what you hope to get from it... (if it is that kind of Summer school).
Personally, I wouldn't try too say much - just smile - introduce yourself - saying something like the above : )
Hope this helps!