"The content you wanted to modify was too big or small to fit on the canvas"

Please help me. I get this message when i'm trying to resize some object. I need this present on Thursday for a school exam, so i really need your help.
Can you solve my problem? Thank you so much.
This is my Prezi URL: http://prezi.com/spjs_rsi2acq/edit/#3...

Giorgia