Ok let's make it simple!
I will show you step by step how to custom your CSS, That will solve your trouble.
Take care to follow precisely ALL steps.
1° Go to the Components -> HikaShop -> Configuration
2° Click on "Display" tab
3° Click on CSS
4° Here, on Front-end CSS File you must have selected "old" BUT if not, select it!
5° Click on the little pen/ "edit" icon
6° Copy & Paste this code :
/*ADD CSS CODE HERE !!! */
.pane-sliders .panel {
border: 0px solid #E5E5E5;
}
div#category_panel_181 h3 {
font-size: 100% !important;
}
/* CUSTOM END */
AND don't forget to save !!!
If I'm right your issue will be solve with this.
Regards,