Mobile Responsiveness

In the third section of mentioned website I am using a contact form 7 which is being styled by cf7 style plugin. By default it should have the ability to adjust its width according to row or column of drag and drop builder and button alignment must also be present but there’s no option to place button in center.
I adjuested these settings by setting margins and paddings and setting input width.
But Main Point is these settings aren’t suitable for mobile and vice versa. So anybody can help me with this ?

The page I need help with: [log in to see the link]