1. The mode.
2. There should be a little button in the left bottom corner. You click on that twice, and it should focus better.
3. Make sure your lens is clean too
Is this happening in all apps (FB, WhatsApp, etc.) which uses camera or just the camera app?
if it's happening in all apps then it could be the hardware having issues. In such case visit UBreakIFix for a check up (Batteries Plus is another option).
Please share the device's model number, software version and the camera app's version, thanks.
If there is no issue with the hardware and it's only happening at Camera app, then reproduce the issue and submit error report to Samsung Members for additional help.