need help to modify this push button code

Using Arduino Programming Questions
14

Your code is not updating the value of currentState when you change screens so it will always be the same value.

Look at this again

Screen 1 on display. currentState = 1
button 1 pressed. Set currentState to 2 and show screen 2
button 2 pressed. Set currentState to 3 and show screen 3
button 3 pressed. Set currentState to 4 and show screen 4

NOTE - I deliberately referred to screens rather than menus because when updating a fingerprint, for example, there will not be a menu on the screen, rather a prompt asking for the user to put their finger on the device or press a button to exit. Equally, when a fingerprint has been read you probably need a screen asking for confirmation, but that is up to you.