@rajendarbandari since iFixit does not have a guide, yet use the one [https://www.sosav.fr/guides/mobiles/xiaomi/xiaomi-redmi-5/batterie|from here] It is written in French but Chrome and other browsers do a pretty good job of translating it.
Replacement batteries are readily available online. Just pick a vendor that appeals to you.
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.