Javascript toggle/show layers Acrobat DC

Hello folks,

I need some assistance by toggling the visibility of layers. I am not to familiar with JS yet but i managed at least to show single layers depending on what is selected from a list. The layers hold descriptions in English, German and French language. This layers are shown if i put in the following code into the validation field:

var layers = this.getOCGs();
var v = event.value;
for (var i = 0; i < this.layers.length; i++) {
if (layers[i].name == "Deutsch" && v == "Deutsch") {
layers[i].state = true
}
else if (layers[i].name == "English" && v == "English") {
layers[i].state = true;
}
else if (layers[i].name == "Francais" && v == "Francais") {
layers[i].state = true;
}
else {
layers[i].state = false;
}
}

How do I manage to show another layer named "Hintergrund" (German for Background) all the time, no matter which of the language selections has been made?

Thank you in advance for your kind support!

Matthias