The 'Responsive' theme (https://wordpress.org/themes/responsive) is designed to respond to the device you are using. It does this by changing the navigation, collapsing the content and moving the widgets to the bottom (on mobile). This provides your mobile users with a better experience than simply serving them the desktop site.
This is a desirable feature for a site on the modern web so I am not sure you want to remove it.
Is it possible you have installed a mobile plugin that is drastically changing the way your theme looks and behaves?
A link to your site would be very helpful to understand what you want to achieve.
