I was glued to the wall. I want to remove it with breaking it. It large 4x10 feet.

The entire mirror (4x10 feet) is glued to the wall?

(I trust you didn't mean you are glued to the wall.)

Obtain a length of small, stranded cable. The smallest diameter cable you can find. It has to stranded, (little wires making up the cable). Also get a short piece 3/4 diameter dowel. Cut off two pieces of the dowel about three inches long and drill a hole the center of each piece. These will be your handles for the cable. Run the cable through the holes and tie it to the handles.
You will need three people to assist you. One to help you saw and two to hold the mirror as you cut the glue.

Slip the cable between the mirror and the wall and pull the cable back and forth in a sawing action. The cable will cut the glue. The cable needs to be two or three foot longer than the way you are going to cut. If you can cut the four foot way, the cable needs to be about 7' long. If you are going to cut the 10' way it needs to be about 13' long.

Small diameter, stranded cable.

You can also use a blow dryer on the mirror while sawing the glue. The sell the small stranded cable at home depot and Lowe's.