Is there a pulllup or pulldown on your button?
Best practice: change this line
pinMode(buttonPinEnter, INPUT);
to
pinMode(buttonPinEnter, INPUT_PULLUP);
and have your button connect the pin to Gnd when pushed.
Then check for a LOW and act on that - button will read HIGH when not pushed.
// (i.e. the input went from LOW to HIGH), and you've waited
changes to
// (i.e. the input went from HIGH to LOW), and you've waited