I've tried getting help from other examples online but I still couldn't get it working properly, and now it seems to freeze after running for only a second or two! I have three classes as well as my main. Can anyone help?

MAIN


alien myalien;
humans[] myhumans;
int totalHumans = 0;
Timer mytimer;

boolean gameOver = false;

int score = 0;
int level = 1;
int lives = 10;
int levelCounter = 0;

PFont f;

PImage img;

void setup() {
  size(800, 600);
  smooth();
  img = loadImage("space_cat.jpg");
  background(img);
  myalien = new alien();
  myhumans = new humans[50];
  mytimer = new Timer(3000);
  mytimer.start();
  f = createFont("Arial",12,true);
}



void draw() {
  if (gameOver)  {
    textFont(f,48);
    textAlign(CENTER);
    fill(0);
    text("GAME OVER",WIDTH/2,HEIGHT/2);
  }
  else {
  myalien.display();
  myalien.move();
  if (mytimer.isFinished()) {
    if (totalHumans < myhumans.length) {
      myhumans[totalHumans] = new humans();
      totalHumans++;
    }
    mytimer.start();
  }
  for (int i = 0; i < totalHumans; i++) {
    if (finished = true) {
      myhumans[i].move();
      myhumans[i].drawBody();
      if (myhumans[i].reachedBottom()) {
        levelCounter++;
        myhumans[i].finished();
        lives--;
        if (lives <= 0) {
          gameOver = true;
        }
      }
      if (myalien.intersect(myhumans[i])) {
        myhumans[i].finished();
        levelCounter++;
        score++;
      }
    }
  }
  if (levelCounter >= myhumans.length) {
    level++;
    levelCounter = 0;
    lives = 10;
    mytimer.setTime(constrain(300-level*25,0,300));
    totalHumans = 0;
  }
  textFont(f,14);
  fill(0);
  text("Lives left: "+ lives,10,20);
  rect(10,24,lives*10,10);
 
  text("Level: "+ level,300,20);
  text("Score: "+ score, 300,40);
  }
}



-------------------------------

class Timer {
 
  int savedTime;
  int totalTime;
 
  Timer(int tempTotalTime) {
    totalTime = tempTotalTime;
  }
 
  void setTime(int t) {
    totalTime = t;
  }
 
  void start() {
    savedTime = millis();
  }
 
  boolean isFinished() {
    int passedTime = millis() - savedTime;
    if (passedTime > totalTime) {
      return true;
    } else {
      return false;
    }
  }
}




-----------------------------


class alien {
 
  float bodyXLoc;
  float bodyYLoc;
  int bodyWidth;
  int bodyHeight;

  int headWidth;
  float headHeight;
  float headXLoc;
  float headYLoc;
  int eyeWidth;
  int eyeHeight;

  int speed;
 
  int direction;
 
 
  alien () {
    bodyXLoc = 450;
    bodyYLoc = 300;
     bodyWidth = 50;  //changes width of the body
     bodyHeight = 100;  //changes height of the body
     headHeight = 100;
     eyeWidth = 30;  //changes the width of the eyes
     eyeHeight = 30;  //changes the height of the eyes
     speed = 5;  //changes how fast the alien moves
     direction = 1;
  } 
 

 
//  void setLocation(float tempX, float tempY)  {
//    bodyXLoc = tempX;
//    bodyYLoc = tempY;
//  }
 
  void display() {
    //Draw body
    stroke(0,0,0);
    strokeWeight(1);
    fill(137,242,204);  //defines the colour for the alien's body
    rect(bodyXLoc, bodyYLoc, bodyWidth, bodyHeight);  //draws the aliens body
    stroke(255,255,255);  //defines the colour of the alien's arms
    strokeWeight(8);  //defines the thickness of the alien's arms
    line(bodyXLoc+51, bodyYLoc+30, bodyXLoc+100, bodyYLoc+70);  //draws the arms
    line(bodyXLoc+51, bodyYLoc+50, bodyXLoc+100, bodyYLoc+90);
    line(bodyXLoc+51, bodyYLoc+70, bodyXLoc+100, bodyYLoc+110);
    line(bodyXLoc, bodyYLoc+30, bodyXLoc-50, bodyYLoc+70);
    line(bodyXLoc, bodyYLoc+50, bodyXLoc-50, bodyYLoc+90);
    line(bodyXLoc, bodyYLoc+70, bodyXLoc-50, bodyYLoc+110);
    line(bodyXLoc+10, bodyYLoc+100, bodyXLoc+10, bodyYLoc+150);
    line(bodyXLoc+25, bodyYLoc+100, bodyXLoc+25, bodyYLoc+150);
    line(bodyXLoc+40, bodyYLoc+100, bodyXLoc+40, bodyYLoc+150);

    //Draw head
    fill(137,242,204);  //defines the colour of the alien's head
    stroke(0);  //defines the colour of the outline of the alien's head
    strokeWeight(1);  //thins the line around the head
    headWidth = bodyWidth*2;  //defines the width of the head
    headXLoc = bodyXLoc+25;  //defines the location where the head is drawn
    headYLoc = bodyYLoc+5;  // ""
    ellipse(headXLoc, headYLoc, headWidth, headHeight);  //draws the head
    fill(255,255,255);  //defines the colour of the eyes
    ellipse(headXLoc-10, headYLoc-15, eyeWidth+10, eyeHeight+10);  //draws the first eye
    ellipse(headXLoc+25, headYLoc-5, eyeWidth-10, eyeHeight-10);  //draws the second eye
    fill(0,0,0);  //defines the colour of the pupils
    ellipse(headXLoc-10, headYLoc-15, eyeWidth/2+10, eyeHeight/2+10);  //draws the first pupil
    ellipse(headXLoc+25, headYLoc-5, eyeWidth/2-10, eyeHeight/2-10);  //draws the second pupil
    ellipse(headXLoc+10, headYLoc+20, eyeWidth/2, eyeHeight/2);
  }

 

  void move() {
    if(direction==1){
      bodyXLoc = bodyXLoc + speed;
    }
    if(direction==2){
      bodyYLoc=bodyYLoc-speed;
    }
    if(direction==3){
      bodyXLoc=bodyXLoc-speed;
    }
    if(direction==4){
      bodyYLoc=bodyYLoc+speed;
    }
    if(bodyXLoc<0||bodyXLoc>690||bodyYLoc<0||Y>690){
      speed=0;
      }
  }

  void keyPressed(){
  if(keyCode==UP){direction=2;}
  if(keyCode==LEFT){direction=3;}
  if(keyCode== DOWN){direction=4;}
  if(keyCode== RIGHT){ direction=1;}
}


  boolean intersect (humans h)  {
    float distance = dist(bodyXLoc, bodyYLoc, h.bodyXLoc, h.bodyYLoc);
    if (distance < bodyWidth + h.bodyWidth)  {
      return true;
   } else {
     return false;
   }
  }
}




--------------------------------


class humans {
 
  int bodyXLoc;
  int bodyYLoc;
  int bodyWidth;
  int bodyHeight;

  int headWidth;
  float headHeight;
  int headXLoc;
  int headYLoc;
  float headheight;
  int eyeWidth;
  int eyeHeight;

  int speed;
 
 
  humans () {
     bodyXLoc = int(random(1,width));  //randomly generates the start position of the humans
     bodyYLoc = 1;  //ensures the humans are generated at the top
     bodyWidth = 10;  //changes width of the body
     bodyHeight = 20;  //changes height of the body
     speed = int(random(1,2));  //changes how fast the humans move
  } 
 

  void move() {
    bodyYLoc += speed;  //makes the humans move downwards
  }
    boolean reachedBottom() {
    if (bodyYLoc > height + bodyHeight) {
      return true;
    } else {
      return false;
    }
  }

  void drawBody() {
      fill(255,0,0);  //defines the colour for the human's body
      rect(bodyXLoc, bodyYLoc, bodyWidth, bodyHeight);  //draws the body
      stroke(255,0,0);
      strokeWeight(2);
      line(bodyXLoc+10, bodyYLoc+5, bodyXLoc+20, bodyYLoc+10);
      line(bodyXLoc, bodyYLoc+5, bodyXLoc-10, bodyYLoc+10);
      line(bodyXLoc+10, bodyYLoc+20, bodyXLoc+15, bodyYLoc+30);
      line(bodyXLoc, bodyYLoc+20, bodyXLoc-5, bodyYLoc+30);
      ellipse(bodyXLoc+5, bodyYLoc-5, bodyWidth, bodyWidth);
    }
   
  void finished() {
      finished = true;
    }
   
}