Sorry, this is not what i mean.
The Footer Above Module and other Module positions i can divide as i like. No problem at all.
However what i mean are the three positions that are kind of integrated in the footer and are modulepositions : LeftFooterArea, CenterFooterArea and RightFooterArea. These are not shown in module positions in the GUI but can be used and selected in Joomla in the TT-template. I would like to change the width of these areas in a way that the right column is wider on mobile screens.