This behavior is normal, as it is based on the design and coding of CSS of the responsive theme. Rendering images in mobile usually doesn't show a smaller version from the full image( resize). The same with objects. You need keep playing around with blocks and content to reach a design that you like. or you can modify the CSS for mobile view to fit your needs. Website builder odoo and others have limiations. 

Note that, this is a paid theme and should be supported by the vendor, just contact thier support.