Keypad calculator with latching button - button

Question

I am writing a code for Arduino calculator and I would be thankful for your help. I have defined a 2x7 keypad, consisting of numbers from 0 - 9 and 4 math operations (+,-,*,/). I have included Keypad.h library. I am using LATCHING buttons for input. Everytime I press a button it stays locked in. If i want to turn a button OFF, I have to press it again to release it from ON state. I get input displayed on OLED Arduino display. There lies a problem in my code, because when I press a button I get number displayed on display, but then I have to turn OFF the same button and press another one to get the next number/operation displayed. How can I change the code so that I don't need to turn off the button to press another one and get its value displayed on the screen? Thank you for your help in advance!
See the code bellow:
#include <Keypad.h>
#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
const byte numRows= 2; //number of rows on the keypad
const byte numCols= 7 ; //number of columns on the keypad
//keymap defines the key pressed according to the row and columns just as appears on the keypad
char customKey = 0;
double first = 0;
long second = 0;
double total = 0;
char Operator;
bool equalPressed=false;
bool showFirst = false;
char keymap[numRows][numCols]=
{
{'0', '1', '2', '3', '4', '5', '6'},
{'7', '8', '9', '+', '-', 'x', '/'}
};
//initializes an instance of the Keypad class
byte rowPins[numRows] = {2,3}; // definiraj pine ko zvezeš gumbe!!
byte colPins[numCols]= {4,5,6,7,8,9,10}; // definiraj pine ko zvezeš gumbe!!
Keypad customKeypad= Keypad(makeKeymap(keymap), rowPins, colPins, numRows, numCols);
void showSplash() {
String splashString="WELCOME";
display.clearDisplay();
display.setTextSize(1);
display.setTextColor(WHITE);
display.setCursor(0,0);
display.setCursor(64-(splashString.length()*3),0);
display.print(splashString);
display.setTextSize(2);
splashString="MATEJ";
display.setCursor(64-(splashString.length()*6),16);
display.print(splashString);
display.setTextSize(2);
splashString="ALEN";
display.setCursor(64-(splashString.length()*6),40);
display.print(splashString);
display.display();
delay(3000);
}
void setup()
{
Serial.begin(9600);
display.begin(SSD1306_SWITCHCAPVCC, 0x3C); // initialize with the I2C addr 0x3D (for the 128x64)
showSplash();
display.setTextSize(2);
display.clearDisplay();
display.display();
}
void loop(){
customKey = customKeypad.getKey();
switch(customKey)
{
case '0' ... '9': // This keeps collecting the first value until a operator is pressed "+-*/"
showFirst=true;
first = first * 10 + (customKey - '0');
showDisplay();
break;
case '+':
showFirst=true;
Operator='+';
showDisplay();
second = SecondNumber(); // get the collected the second number
total = first + second;
showDisplay();
first = total, // reset values back to zero for next use
second = 0;
break;
case '-':
showFirst=true;
Operator='-';
showDisplay();
second = SecondNumber();
total = first - second;
showDisplay();
first = total, second = 0;
break;
case 'x':
showFirst=true;
Operator='x';
showDisplay();
second = SecondNumber();
total = first * second;
showDisplay();
first = total, second = 0;
break;
case '/':
showFirst=true;
Operator='/';
showDisplay();
second = SecondNumber();
second == 0 ? display.print("Invalid") : total = (float)first / (float)second;
showDisplay();
first = total, second = 0;
break;
}
}
void showDisplay()
{
display.clearDisplay();
display.setCursor(110,0);
display.println(Operator);
if (showFirst) {
Serial.print(first);
display.println(first);
} else
{
display.println("");
}
if (second>0) {
display.println(second);
} else
{
display.println("");
}
if (equalPressed) {
display.println(total);
equalPressed=false;
}
display.display();
}
long SecondNumber()
{
while( 1 )
{
customKey = customKeypad.getKey();
if(customKey >= '0' && customKey <= '9')
{
second = second * 10 + (customKey - '0');
showDisplay();
}
}
return second;
}