Obviously, because you lack all the basics. And that’s why a javascript course that starts at 0 would help you massively.
Unfortunately, we can neither here in the forum, nor by mail respond to each of your Javascript problems, unless it is a Bricks bug. And that is simply not the case here.
Another small hint: you already have several EventListeners in your JS code, each listening for a Click Event. Copy one of them and make it listen to your submit button.