Your code
<p style="text-align: center;"><img class="img-responsive" style="width: 100%;" src="https://www.fireandbox.it/img/cms/ck8560/1.jpg" alt="2click car" width="1170" height="auto" /></p>
Must be:
<p style="text-align: center;"><img class="img-responsive" style="width: 100%;" src="https://www.fireandbox.it/img/cms/ck8560/1.jpg" alt="2click car" width="100%" height="auto" /></p>
Check also this:
<p style="text-align: center;"><img class="img-responsive" style="width: 100%; margin-left:-15px; margin-right:-15px" src="https://www.fireandbox.it/img/cms/ck8560/1.jpg" alt="2click car" /></p>
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Prestashop adds width and height tags in px, but you need always to change it to % in other case you will always have overflowed image on mobile view