Hi,

Use this custom css

#mod-speasyimagegallery-113 .speasyimagegallery-row{
    margin:0px !important;
}

Note: Path towards custom CSS: Extensions>Templates>Styles> Click on your current default template name then choose Template Options. Then find custom CSS within the custom code.

I think it will solve your issue. Please let me know is it ok or not

https://prnt.sc/1yvog58

-Regards