How to slow down my Variable Timestep Loop in Java

I am currently developing a game in Java and I ran into a problem

At first, I thought my game loop was working well as it was giving a similar amount of FPS as the tutorial I was following

Then I reach to the phase where I started implementing input from the user. When the user entered in the W key the sprite would move very rapidly to the bottom of the screen and then back up to the top for no explained reason

I think it is something to do with my game loop. As I did my research I deduced that my game loop is running way to fast. The only problem is that I haven't been able to slow down the loop. Or maybe it is a totally different problem

Can anyone please help

Run method of my game:

public void run() {
    long lastTime = System.nanoTime();
    double amountOfTicks = 60.0;
    double ns = 1000000000 / amountOfTicks;
    double delta = 0;
    long timer = System.currentTimeMillis();
    int frames = 0 ;

    /*  Game loop use:
     *      From timer calls to while loops to recursive function calls to keep the game alive 
     *      Until a certain condition is meet (The loop)
     * 
     *      A way to delay the length of each loop iteration so you get a stable frame rate (The timing mechanism) 
     *  
     *      A way to make the game speed remain independent of the speed of the loop (The interpolation)*/

    //This is a variable timestep loop
    while (running) {
        long now = System.nanoTime();
        delta += (now - lastTime) / ns;
        lastTime = now;
        while (delta >= 1) {
            tick();
            delta--;
        }
        if(running)
            render();
        frames++;

        if(System.currentTimeMillis() - timer > 1000) {
            timer += 1000;
            System.out.println("FPS: " + frames);
            frames = 0;
            //While times updated per second is greater than one (allowing updates to be seen) call tick method of Handler class


            /* Fixed timestep loops vs Variable timestep loops:
             * 
             *      Variable timestep loops: Great because the game will seem consistent regardless of how fast the players's computer is
             *          Allowing it to work on a variety of machines and update the game logic with very high attention to details happening in the game 
             *          Graphics latency is not a problem as things are drawn as they change
             * 
             *      
             *    
             *      Fixed timestep loops: You know that every single timestep 
             *          will take up the exact same length of time. Allows for consistent gameplay 
             *          regardless of how fast a machine is as you know the tick rate of your machine
             *          Works wonderfully for math-heavy games with physics operations. Also good for networked games as packets are going and coming at a generally constant speed.
             *          Keeps game logic running at a very low rate while the frame rate can still and frame rate really high 
             *                                                            */
        }
        stop();
    }
}

'''

Thanks!!!