Software problems

On my iPhone 6 plus 64gb I've been having problems with tons of app crashes and when I switch from an app to home screen my status bar(where the time is) goes real dim where I can't see it. I brought it into the Apple Store and they told me to restore it and I did just that yesterday and I'm getting the same problems. My question is do I deal with it or should I go back and ask for a new phone? It seems like now they aren't so fast to give you a new phone as in years past. My wife had battery drainage problems and they told her to do the same thing, restore the software bc of buggy apps.

What should I do?