Can the battery be replaced/fixed?

@muhammadnaqib yes it can but it's not easy. The challenge will be to open the device. Check on videos like this to get an idea of what is involved. Depending on your device model, do an online search for the battery ones you have it open and can read the numbers on the battery. If you are stuck or see something that requires more info/help, post some pictures of that with your Question. Adding images to an existing question

While you work on your device, 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.

Repair is War on Entropy!