I've stolen these pictures from a random ebay auction...
As you've shown, you have a black door panel with a colored leather insert. If you look at the picture of the back of the door panel, you can see that the door panel is held in by black plastic plugs.
Now, the plastic plugs are a little annoying. BMW basically hot riveted the panel in place by melting the plastic. But you can remelt and apply some adhesive in a swap.
It doesn't hurt to try to stretch your current panel back into shape, but I don't expect you to succeed. The panel swap is how you move forward after that.
