Why my device heating so much

@shivanjaysoni this will depend on when it heats up. If it does so while you are using it it is possibly a software issue. Make sure you have the latest software installed and make sure that you have not to many Apps running in the background. Make sure that you have your Network settings optimized. Playing games and watching video uses most of the processing power. That can heat up your phone as well.

Should it heat up despite all of those things having been correctly set, then the issue can be with the battery. If power demands are to great on it, it will discharge to fast and that creates heat. I would suggest that you replace the battery and then re-evaluate. Since iFixit does not yet have a specific guide for this use something like this video Replacement batteries are readily available at many online stores.

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 issues with their device. 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!