Nano + LCD + Hall sensor. Need help with code.

Thanks for reply. Edited code:

// --------------------------------------------------------------------------
#include <LiquidCrystal.h>

// ekrano pajungimo pinai
LiquidCrystal lcd(12, 11, 10, 9, 8, 7);

//kintamieji
float seklosLikutis = 2000.0;
float pasetasPlotas = 0;

volatile unsigned long cnt=0;
unsigned long previousMillis = 0;     
const long interval = 1000;  

//jutiklis
const int hallPin = 2; // pin 2 = int 0

//reiksmes
float normaPerSuki = 0.1095;
float plotasPerSuki = 0.0476;

char str1[15];
char str2[15];
// --------------------------------------------------------------------------

void doCount() // interrupt callback should be as short as possible!
{
  if(digitalRead(hallPin) == LOW)
  {
    cnt++;
    pasetasPlotas = plotasPerSuki + pasetasPlotas;
    seklosLikutis = seklosLikutis - normaPerSuki; 
  }
}

// --------------------------------------------------------------------------
void setup() 
{
  lcd.begin(16, 2);
  lcd.setCursor(1,0);
  lcd.print("Vaderstad Rapid");
  lcd.setCursor(2,1);
  lcd.print("Versija 1.0");
  delay(1000);
  lcd.clear();
  
  pinMode(hallPin,INPUT_PULLUP);
  digitalWrite(hallPin,HIGH);
  attachInterrupt(digitalPinToInterrupt(hallPin), doCount, FALLING);  // hall pin on interrupt 0 = pin 2
  digitalWrite(hallPin,HIGH);
  pinMode(hallPin,INPUT_PULLUP);
}
// --------------------------------------------------------------------------

void loop()
{
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= interval) 
  {
    previousMillis = currentMillis;
    
    dtostrf(pasetasPlotas,7, 4, str1);
    dtostrf(seklosLikutis,7, 4, str2);
    
    lcd.setCursor(0,0);
    lcd.print("Plotas:");
    //lcd.setCursor(8,0);
    lcd.print(str1);
    lcd.print("a");
    lcd.setCursor(0,1);
    lcd.print("Sekla:");
    //lcd.setCursor(7,1);
    lcd.print(str2);
    lcd.print("kg");
    //lcd.print("Apsisukimai:");
    //lcd.setCursor(13,1);
    //lcd.print(cnt);
  }          
}

// --------------------------------------------------------------------------