How to accelerate and improve the rendering on iPhone ?

Hello everybody ! I've just made a 3D game for iPhone and iPad platform, I've bought the license, I've built it on XCode and I've tested it on my iPhone. The problem is that it takes too much time to load each scene and I can't even play because it's too slow and it would perhaps be about 1 frame per second ! I tested it again on my computer and it worked perfectly. I deleted some heavy objects and tried again but it is the same thing : I still can't play. How can I accelerate and improve the speed and the rendering ? Is it any simple solution or do I have to buy Unity Pro ? Thank you very much. Maroun Eddé.