128x64 LCD and pushButtons

Could someone give me some advice related to building a menu for a 128x64 LCD using 5 pushButtons?
i have 5 screens.
btn1 is for display MainMenu and Selection.
btn2 and btn3 is for up and down scrolling
btn 4 and btn4 is for switching on/off and increase decrease values.

the problem which i encounter is related to btn2 and btn3.
i don;t know how to use them for scrolling in in another screen except screen1 (MainMenu).

#include "U8glib.h"
U8GLIB_ST7920_128X64_1X u8g(13,12,11); //Enable, RW, RS, RESET

int selectionButton = A1, selectionButtonState, selectionButtonLastState = 0, cntSelectionButtonPressed = 0, cntSelectionButtonPressed2ForMenu2 = 0;
int menuButton = A0, menuButtonState, menuButtonLastState = 0;
int scrollDownButton = A3, scrollDownButtonState, scrollDownButtonLastState = 0;
  boolean mainMenu = false;


void setup()
{
    Serial.begin(9600);
    if ( u8g.getMode() == U8G_MODE_R3G3B2 ) 
    u8g.setColorIndex(255);     // white
    else if ( u8g.getMode() == U8G_MODE_GRAY2BIT )
    u8g.setColorIndex(3);         // max intensity
    else if ( u8g.getMode() == U8G_MODE_BW )
    pinMode(selectionButton,INPUT);
    pinMode(menuButton,INPUT);
    pinMode(scrollDownButton,INPUT);

}

void loop()
{
  
 scrollDownButtonState = digitalRead(A3);
 selectionButton = digitalRead(A1);
 menuButton = digitalRead(A0);



//pin A1 = RiGHT
 if(selectionButton != selectionButtonLastState)
 {
  if(digitalRead(A1) == HIGH)
  {
    cntSelectionButtonPressed += 1;
    if(cntSelectionButtonPressed == 4)
    {
      cntSelectionButtonPressed = 0;
    }
  }
  selectionButtonLastState = selectionButton;
 }


////////////////////////
 if(menuButton != menuButtonLastState)
  {
    if(cntSelectionButtonPressed == 1 && digitalRead(A0) == HIGH)
    {
         cntSelectionButtonPressed2ForMenu2 += 1; 
    }
      if(cntSelectionButtonPressed2ForMenu2 == 4)
      {
        cntSelectionButtonPressed2ForMenu2 = 0;
      }
       u8g.firstPage();
       do{
           Menu2();
         }while(u8g.nextPage());
   
    
       menuButtonLastState = menuButton; 
  }
 else
 {
 u8g.firstPage();
  do{
    MainMenu();
  }while(u8g.nextPage());
 }
 
}


void MainMenu(){
switch(cntSelectionButtonPressed)
{

  case 1:
           u8g.setFont(u8g_font_6x13); 
           u8g.setPrintPos(15,15);
           u8g.print("> Ceas");
           u8g.setPrintPos(15,25);
           u8g.print("  Interior casa");
           u8g.setPrintPos(15,35);
           u8g.print("  Exterior casa");  
           break;
  case 2:     
           u8g.setFont(u8g_font_6x13); 
           u8g.setPrintPos(15,15);
           u8g.print("  Ceas");
           u8g.setPrintPos(15,25);
           u8g.print("> Interior casa");
           u8g.setPrintPos(15,35);
           u8g.print("  Exterior casa");  
           break;
           break;
  case 3:
           u8g.setFont(u8g_font_6x13); 
           u8g.setPrintPos(15,15);
           u8g.print("  Ceas");
           u8g.setPrintPos(15,25);
           u8g.print("  Interior casa");
           u8g.setPrintPos(15,35);
           u8g.print("> Exterior casa");  
           break;   
}
}



void Menu2()
{
  
  switch(cntSelectionButtonPressed2ForMenu2)
{
  case 1:
           u8g.setFont(u8g_font_6x13); 
           u8g.setPrintPos(15,15);
           u8g.print("> Stil1");
           u8g.setPrintPos(15,25);
           u8g.print("  Stil2");
           u8g.setPrintPos(15,35);
           u8g.print("  Stil3");  
           break;
  case 2:     
           u8g.setFont(u8g_font_6x13); 
           u8g.setPrintPos(15,15);
           u8g.print("  Stil1");
           u8g.setPrintPos(15,25);
           u8g.print("> Stil2");
           u8g.setPrintPos(15,35);
           u8g.print("  Stil3");  
           break;
           break;
  case 3:
           u8g.setFont(u8g_font_6x13); 
           u8g.setPrintPos(15,15);
           u8g.print("  Stil1");
           u8g.setPrintPos(15,25);
           u8g.print("  Stil2");
           u8g.setPrintPos(15,35);
           u8g.print("> Stil3");  
           break;   
}
}

Forget the buttons for a moment, and explain how the program should scroll the screen.

Then explain how the buttons should be pushed, in order to scroll the screen.

Also post a wiring diagram, or explain how the buttons are wired to the Arduino.