It's not just the screen and the stereo, there are differences in the general wiring of the car, the little screen between the speedometer and revs is different, the center console has more buttons...
In addition, you are trying to install equipment designed 13 years ago and that in electronics means outdated.
With the small screen that you have, millions of Citroen and Peugeot cars were manufactured and there are solutions on the market to replace the stereo with an Android screen, perhaps you should think about this alternative.