Hi,
As you configuration screenshoot shows, you set that the image height must be 400px.
So HikaShop put some CSS to force that height ; but when you're in responsive, the responsive CSS change the image width without touching his height, which generate your "issue".
Clean up your menu settings and it should be better.
For the rest, that documentation would be interesting for the CSS customizations (I did nothing more that what I told you to do in my previous message)
www.hikashop.com/support/documentation/1...the-display.html#css
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.