Curious how this is working out for you.
I have a D610 and while there are a few basic things you need to know, with a properly working AF lens and AF on, and adequate light for the lens, ISO, etc then focus is never an issue for me. If I mess with manual everything I mess up some of the time. On AP I'm pretty good at getting the shot. On some of my vintage glass in tricky situations the lens may hunt for the right focus for a moment - but learn to watch for the in focus light in the view finder (took me a while to learn about that focus indicator) and if enabled it should also 'beep' when focus locks on.
One of my bad habits is forgetting to return the settings to "normal" after a shoot. For example turning on the bracket to do a HDR series, and then forget to turn it off. Or adjust the exposure compensation, and leave it. and other similar bad habits. I did play with the U1 and U2 settings to a 'return to normal' but even then I have to remember to flip to them.
I've had my camera a year now and I'm still just learning. Lots to learn.
Do post your efforts and get some comments based on the EXIF info.
Don't give up, the 600 is a grand bit of tech.