How can I fix the finger print

@zmlaouhi first you need to rule out the most common software/firmware issues. For that use this site If none of that worked, it is possible that this is a bad sensor. To replace it follow 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.