@zmlaouhi first you need to rule out the most common software/firmware issues. For that use [https://www.samsung.com/uk/support/mobile-devices/my-fingerprint-scanner-isnt-working/|this site] If none of that worked, it is possible that this is a bad sensor. To replace it follow [https://www.nadiemellamagallina.com/en/manuales/smartphones-1/samsung-4/samsung-galaxy-a13-sm-a137-1378/flex-de-sensor-de-huella-y-encendido-12476|this guide] It is written in Spanish but browsers like Edge or Chrome do a great job translating it.
While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.