You need to use conditional product attributes to make the value of one attribute dependant on another. Click on the View/Edit condition link for the model attribute shown on your last image.
That does not work because the condition is that if I select lets say "Apple" the Model dropdown will appear otherwise it will not appear but that is not what I want.
What I want is if I select "Apple" in the first dropdown. "Iphone 5" should be the only option in the Model dropdown.
That does not work because the condition is that if I select lets say "Apple" the Model dropdown will appear otherwise it will not appear but that is not what I want.
So you create two product attributes, one called Apple models and one called Samsung models. You make the display of the Apple models attribute dependant on the selection of the Apple brand option and the Samsung models attribute dependant on the selection of the Samsung brand option.