Adobe Acrobat Pro Dc opens multiple tabs and multiple windows

Hello

I have the version 15.010.20056.36345 and chose "open documents as new tabs in the same window" so I can easily switch between multiple documents. But the problem is that it also opens multiple windows. When I go to "Taskbar Settings" and choose to never combine taskbar buttons the problem is almost solved. But when I put the mouse pointer on the single window it still shows me a preview of all available documents. Like this

but choosing "never combine taskbar buttons" is not a real solutions since it does't look good. I want to have all taskbar items combined.

So I only want that multiple tabs show in one window.

Hope you have a solution for this

thank you