My screen is pretty cracked but it always worked but now my screen is

The Galaxy A5 2017 uses a AMOLED display and these are very fragile. Unlike LCD displays they do not survive cracks in the actual panel and when they crack, they die. You will have to replace the display. Samsung does sell spare parts, so you can get your hands on a original display and the original adhesives for mounting the display on the phone. The repair is very hard one, and only recommended for people with experience.

Samsung Galaxy A5 (2017) Display austauschen