Why does paintComponent not erase past Objects?

Question

Im trying to make a rectangle move on certain Input. Although the Input works, the rectangle is not being redrawn in the way I want it to. The former rectangles are not being erased.

`

public class MiniGame_Panel extends JPanel implements Runnable{

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    Thread gameThread;
    public KeyHandler2 keyH = new KeyHandler2();
    public MGPlayer spieler = new MGPlayer(keyH, this);
    
    public MiniGame_Panel() {
        setBackground(new Color(222, 228, 128, 0));
        setBounds(0, 0, 16*16*3 + 300 + 3, 16*13*3);
        setVisible(true);
        setFocusable(true);
        requestFocus(); 
        
        this.addKeyListener(keyH);
    }

    public void startGameThread() {
        gameThread = new Thread((Runnable) this);
        gameThread.start();
    }

    public void run() {
        double drawInterval = 1000000000/60;
        double delta = 0;
        long lastTime = System.nanoTime();
        long currentTime; 
        
        // GAME LOOP
        while(gameThread != null) {
            currentTime = System.nanoTime();
            delta += (currentTime - lastTime) / drawInterval;
            lastTime = currentTime;
            
            if(delta >= 1) {
                update();
                repaint();
                delta--;
            }
        }
    }
    
    public void update() {
        spieler.update();
    }
    
    
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        
        spieler.draw(g2);
        
        g2.dispose();
    }

}

public class MGPlayer {

    private int x, y;
    private Rectangle rect;
    private int width, height;
    private int leben;
    private KeyHandler2 keyH;
    private MiniGame_Panel mGp;
    
    public MGPlayer(KeyHandler2 keyH, MiniGame_Panel miniGame_Panel) {
        x = 10;
        y = 100;
        width = 50;
        height = 100;
        leben = 3;
        this.keyH = keyH;
        this.mGp = miniGame_Panel;
    }
    
    boolean allowJump;
    public void update() {
        if(keyH.stats) {
            if(!allowJump) {
                this.y -= 8;
            }
            //System.out.println("Leertaste");
        }
        if(keyH.left == true) {
            this.x--;
            //System.out.println("links");
        }
        if(keyH.right == true) {
            this.x++;
            //System.out.println("rechts");
            }
        
        if(y <= 200) {
            this.y++;
            allowJump = true;
        }else {
            allowJump = false;
        }
        
    }
    public void draw(Graphics2D g2) {
        g2.setColor(Color.BLACK);
        g2.fillRect(x, y, width, height);
    }
    
}

`

I just want to draw a rectangle that moves on certain input. This works but instead of redrawing the rectangle, they all stay in the panel.