Size viewed products change

[Spaniarts]

Hello,
 
I'm using the default prestashop template  and want to change the display size of the product.

I mean, when you upload the products, these are listed in small size. If you click on any of them, an 800x800 pixels screen opens and the product appears in the center of the screen but the size remains small. I want the product image fills the screen like in real size.
 
Even better option would be if by openning the box it matches the shape of the product, ie, if I have a triangle, a large triangle is open, if it is a rectangle that opens a big box in a rectangular shape, etc ...
 
In any case both options would be useful. I attach two examples of what is now in prestashop, and what I want.
Could you please tell me how to configure this change?
 
Thank you.