@abdellahamr make sure that all of your settings are geared toward power savings mode. Turn off any Apps that are running in the background. If none of that makes a difference, replace the battery and re-evaluate.
Since iFixit does not yet have a guide for this, use [https://www.nadiemellamagallina.com/en/manuales/smartphones-1/xiaomi-191/xiaomi-redmi-9c-nfc-1363/bater-a-12316|this one] or even a video [https://www.youtube.com/watch?v=Irt1-Vv1Pq4|like this]
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.