Follow this guide to replace a dead or low-capacity battery for the Samsung Galaxy S7 Edge.
'''Before disassembling your phone, discharge the battery below 25%'''. A charged lithium-ion battery can catch fire and/or explode if accidentally punctured.
'''If your battery is swollen, do not heat your phone'''. If needed, you can use a dropper or syringe to inject isopropyl alcohol (90+%) around the edges of the back cover to weaken the adhesive. Swollen batteries can be very dangerous, so wear eye protection and exercise due caution, or take it to a professional if you're not sure how to proceed.