@charansri53, All modern cell phones have the screen bonded to the outer glass with something called OCA, Optically Clear Adhesive. In your case that outer glass is cracked but the LCD and digitizer weren't damaged.
Unfortunately, it takes specialized equipment and expertise to replace the front glass correctly so that it doesn't end up looking like a badly applied screen protector, so almost everyone replaces the complete screen assembly rather than attempting a difficult repair without the proper equipment. If you have a vacuum table to hold the display, guide rods for the separating wire, a vacuum chamber to remove bubbles and a UV chamber to cure the glue, then go for it. Otherwise figure on just replacing the whole screen.
[link|https://www.nadiemellamagallina.com/en/manuales/smartphones-1/xiaomi-191/xiaomi-mi-a1-718/pantalla-completa-6011|Manuales / Xiaomi Mi A1 / Fullscreen|new_window=true]