I would like to position the txt "Meer details over de inschrijving tijdens de opening!" (yellow background)
under the title "Workshop Experimentele Video"(red background.)
The same text should also be aligned next to the picture of the girl with the camera in her hands.
Finally the paragraph next to the picture should move up.
I'm not sure exactly how you want this laid out. You say you want the yellow background text under the title with the red background. Do you mean directly under the title and on top of the image or under the title and to the side of the image and positioned somewhere vertically (e.g. top or bottom).
It seems you want your yellow background to the side of the image but that will leave a gap to the right of the red background if its at the top. But then it doesn't make sense that you have put that yellow text after the paragraph text if you want it to come before.
You'll have to explain a little more clearly (because i'm stupid) and can't quite see what you are doing.
Whichever way you go you will need to float the image left so that the text will rise up alongside.