@khalilgannoun the very first thing you want to do is to change your battery. Since iFixit does not yet a guide for this so go ahead and use something like[https://www.youtube.com/watch?v=eG22nrtuPuQ|this video] to work on your phone.
You also need to close check the flex cable coming from the charging board. Once you have your phone open, I would even go as far as replacing the charging board and the flex since both can be a source of failure as well
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.