Chosen Solution

Two years ago, the rear glass of my iphone smashed. I now use an Otterbox to protect the phone. Wit Otterbox the damage is NOT visible. My issue is that the battery life is now untenable It can’t make it through half the day without the battery running down to 10-20%. Apple says that there is no way to replace the battery because of the rear glass damage and the rear glass cannot be repaired. An independent repair shop said the same. I want to fix the glass and replace the battery. Any ideas on what I can do?

Maybe you could fix the battery by yourself but idk if you could fix the rear glass by yourself (Sorry for my bad english )