Make one button print different sentences on LCD
Consider using what is commonly called in programming as a Finite-state machine.  Advance to the next state each time the button is pressed.  Start out with 3 states and advance to the next after pressing the button.  You many need to double the number of states after adding your message to the program.  This is because you will want to press the button and only print the message once then advance to a new state where all you do is wait for the next button press.

Note, a mechanical device such as a button will need to be de-bounced either in hardware or in software.  This is because the processor may see individual makes and breaks as the button is closed and opened causing it to advance to the next state in unexpected ways.