Noob needing help on code

Hi, Im a noob and I suck at this, but I have gotten this far by trial and error as I attempt to learn. I have a mega hooked up to a 2.4 ili9341 LCD. I am trying to show the numeric analog voltages on the screen. I am stuck and don’t even really know how to really put it into context to search the answer on this one. Ive got the cursor set to the tpVoltage line, but when I start the sketch up, it will briefly show the first reading and then just show blocks. (See attached photo). I have an idea of why its doing that but dont know how what line of code I need to get over the hurdle. I believe that it has to do with the lack of refresh code to show the value as it continuously samples. Can anyone help me?. BTW, looking at my code, I’m sure you’ll see it as quite screwy and may have some tips to make the code a little more efficient(at least I hope). Also, the only line ive attempted to add as a realtime reading thus far is the TP. Ive attached a photo also.
I apologize if I haven’t properly asked this question or if it doesn’t make sense. Im trying my best.

#include <Adafruit_GFX.h> // Core graphics library
#include <Adafruit_TFTLCD.h> // Hardware-specific library

#define LCD_CS A3 // Chip Select goes to Analog 3
#define LCD_CD A2 // Command/Data goes to Analog 2
#define LCD_WR A1 // LCD Write goes to Analog 1
#define LCD_RD A0 // LCD Read goes to Analog 0

#define LCD_RESET A4 // Can alternately just connect to Arduino’s reset pin

// Assign human-readable names to some common 16-bit color values:
#define BLACK 0x0000
#define BLUE 0x001F
#define RED 0xF800
#define GREEN 0x07E0
#define CYAN 0x07FF
#define MAGENTA 0xF81F
#define YELLOW 0xFFE0
#define WHITE 0xFFFF

Adafruit_TFTLCD tft(LCD_CS, LCD_CD, LCD_WR, LCD_RD, LCD_RESET);
#define PENRADIUS 3
#define BOXSIZE 40
#define MINPRESSURE 10
#define MAXPRESSURE 1000

#define tpVoltage analogRead(A8)
#define mapVoltage analogRead(A9)

void setup(void) {
Serial.begin(9600);
tft.begin(0x9341);
tft.setRotation(1);

testText();
int X, Y, Z;

}

void screenSet();
unsigned long testText() {
tft.fillScreen(BLUE);
unsigned long start();
tft.setCursor(60, 0);
tft.setTextColor(YELLOW); tft.setTextSize(3);
tft.println(“LiIVE DATA”);
tft.println();
tft.setTextColor(YELLOW); tft.setTextSize(2);
tft.println(“THROTTLE %”);

tft.println();
tft.setTextSize(2);
tft.println(“MAP: in/Hg”);
tft.println();
tft.println(“RPM:”);
tft.println();
tft.println(“A/F:”);
tft.println();
tft.println(“Speed: mph”);
}

void loop(void) {

tft.drawRect(0, 200, BOXSIZE, BOXSIZE, WHITE);
tft.setCursor(10, 212);
tft.println(“Up”);
void press(boolean p);
boolean isPressed();
boolean justPressed();
boolean justReleased();

tft.drawRect(60, 200, BOXSIZE, BOXSIZE, WHITE);
tft.setCursor(70, 212);
tft.println(“Dn”);
void press(boolean p);
boolean isPressed();
boolean justPressed();
boolean justReleased();

tft.drawRect(120, 200, BOXSIZE, BOXSIZE, WHITE);
tft.setCursor(135, 215);
tft.println("<");
void press(boolean p);
boolean isPressed();
boolean justPressed();
boolean justReleased();

tft.drawRect(175, 200, BOXSIZE, BOXSIZE, WHITE);
tft.setCursor(190, 215);
tft.println(">");
void press(boolean p);
boolean isPressed();
boolean justPressed();
boolean justReleased();

tft.drawRect(240, 200, BOXSIZE, BOXSIZE, WHITE);
tft.setCursor(250, 215);
tft.println(“Ok”);
void press(boolean p);

boolean isPressed();
boolean justPressed();
boolean justReleased();

boolean currstate, laststate;

{
float tpvoltage = tpVoltage * (5.0 / 1023.0);
tft.setCursor(100, 50);tft.setTextSize(2);
tft.println(tpVoltage);
delay(100);

}
Serial.println(mapVoltage);
float mapvoltage = mapVoltage * (5.0 / 1023.0);
//Serial.println(tpVoltage);

}

IMG_0901.JPG