Now after I had tried for 1 hour to connect it to my laptop I've given up.
I was very surprised that the port is specified as HDMI rather than mini-HDMI. After careful, it's a mini-HDMI which is an exclusion criterion for me. Had I known in the front, I never would have ordered it because I mostly used a MacBook and I sure have only a Mini DisplayPort to HDMI cable is (and I now not again wanted to set new cable which cost around 50 euros) this is a no-go. Unfortunately, even if the connection is listed as Philips HDMI on the product page. Now I have my old Acer Netbook rausgekramt (and after what felt like 10 hours Windoze updates) connected to the projector via HDMI to this. Unfortunately, this did not really work. The projector did not recognize my netbook simple. But since I did not want to give up the same, I have not tried the WiFi / DLNA. But again, I came to my limits. The USB stick was then very stupid to me to ultimately I need to connect to my MacBook and not to a USB flash drive.
My conclusion is: not to use cable for my school with MacBook and HDMI. Anyone who has at hand a suitable adapter cable, which may give it a try.
I think the kid is really something in which the source sometimes can be a USB flash drive for the occasional movie night.
The one star I forgive, because it is really very handy and directly and again goes out. What he should ... not to use the problems between there: /