Hi there and welcome
First, can you go to settings, Applications, then select more then system apps.
Locate camera in the list, press it and press clear data
Let me know if this resolves it please.
When you go to applications John, what do you see in the top right?
you need to choose Applications Manager please.
Then either press on More or swipe to the list All please
yes, but you swipe to the list ALL please
ok, then we will need to factory reset the phone, this will remove all your data and return the phone to new, but we cannot avoid this, so try to backup any personal data you wish to keep first.
Then go to Settings, Backup and Reset, Factory Data Reset
Complete this and once done, setup the S5 again and tell me how it now operates please.
Thank you John