Change a Prestashop CSS file and adjust one form size.

Hello, Need someone to disable the responsiveness of the default theme on Prestashop 1.6, we need for the website to show the same way on desktops, mobile and tablets. We also need for this change to be reversible so when Prestashop actually comes with a solution to the poor responsiveness we can change it back. This is done by editing a CSS file but we dont know exactly how to go about it And we need to change the size of a form on the front end of the website so that people do not need to scroll form size to size to read the full document. It needs to be done ASAP. Thanks