5s randomly shuts down and camera shutter sound even when in silent mode

Hello Everyone,

I have a 5s that is refurbed and I noticed that there were three problems: it shuts down randomly even when there's power left, the camera shutter sound is heard even if it was in silent mode, and I can't send pictures to people who are not iphone users. Any ideas on how to fix this?

I've tried the hard reset but to no avail.

Thanks for your help in advance 🙂