As a DIY repair the only thing to do now is to open the phone and first inspect the LCD flex cable connection to the systemboard to ensure that it is secure and hasn’t been jarred loose by the fall.
After that you’ll have to temporarily replace the display to find out whether the problem is in the display itself or in the systemboard.
The LCD display’s internal connections may have been broken because of the fall. It cannot be repaired, the display has to be replaced.
Here’s a link to the ifixit 三星 Galaxy A5 (2017) 屏幕更换 guide, which should be of some help.
The repair is rated as difficult.
Replacement parts (get the complete assembly - LCD screen and digitizer to make it easier) are available online. Just search for Galaxy A5 (2107) LCD screen to get results.
There is a parts link in the guide that you can click on first just to get an idea of the cost etc.
If doing this seems too daunting a task, contact a reputable, professional mobile phone repair service and ask for a quote.