How to open iPhone 3GS with a separating digitizer?

I'm trying to repair my iPhone 3GS, but all the guides say to lift the screen up with a suction cup.

the problem is, its only lifting the front glass panel which I believe is called a digitizer, but the other part of the screen below which is supposed to be attached with adhesive isn't lifting with it

I can't fully take off the front part because I think it's connected with ribbon cables.