Mobile Menu as Pulldown?

Not too sure what you mean - any examples?

sorry Drop-Down Menu -:)

Example: http://schlauchboot-kaufen.eu

This is built in, you just have to set your menu in "Appearance > Editor".

Once the menu is set, drag and indent menu items beneath their parent items to create a dropdown menu.

https://codex.wordpress.org/WordPress_Menu_User_Guide#Creating_Multi-level_Menus

Sorry, I do not understand?

In "Appearance > Menus", drag and drop the menu items to the right under the parent item (the top level menu item). This will create a dropdown menu for you.

More info here:
http://wptavern.com/how-to-create-a-dropdown-menu-of-wordpress-categories-without-using-code
https://codex.wordpress.org/WordPress_Menu_User_Guide#Creating_Multi-level_Menus

You can also YouTube "WordPress dropdown menu" and you'll find quite a few videos showing how to do this :)

This is not that i mean :)

Resize the example Page to Mobile Width and you see what i mean.

Ah, well GP has a built in mobile menu.

However, if you want a select dropdown menu, this plugin may work for you: https://wordpress.org/plugins/jquery-responsive-select-menu/

Yeah, thanks Tom.
But now it shows both :)

How can i disable the Org-GP Mobile Menü?

You can use this CSS:

@media (max-width:768px) {
      .menu-toggle {
            display: none;
      }
}

I use:

@media (max-width:1000px) {
      .menu-toggle {
            display: none !important;
      }
      .main-navigation {
			height: 45px !important;
			padding-top: 15px;
      }
}

Perfect !

Awesome :)