Power off the phone.
Heat up edges to loosen adhesive around.
Heat up the bottom side repeatedly.
Put suction cup on the bottom side.
Insert a guitar pick.
Take away suction cup.
The same way on the other side.
Slide guitar picks to cut adhesive around.
Be careful and patient.
Then lift up the back glass slowly.
Put sticker to a new back glass.
Peel off protective film & make it attach to the back glass.
Peel off other protection film.
Put back Samsung A9 back glass.
Make it fit to the phone well.