Certificate

I have an .ai and I require a background of triangle shapes to start 100% opacity at the top and go to 0% around 2/3rd down the page. I have done some of it just need finishing off

I'll need the red and orange triangles on the left to be hues of different greens and for it to cover down
around 2/3rd of the page. Also the triangles need to peter out so it's not a straight line as per the second drawing.

thanks