Conflicting CSS styling in slider?

Yes, plugin css is conflicting with your theme style. Please check FAQ page to debug your css conflict.
https://nodedesk.zendesk.com/hc/en-us/articles/202243372-How-to-Debug-and-Correct-CSS-Issues-in-Your-Browser

However you can write code to your wp-content/theme/style.css file to override css.

.testimonials-widget-testimonials2 {
  padding: 0;
}

.Testimonials_Widget_Slider_Widget blockquote {
  margin-left: 0;
  margin-right: 0;
}

Thanks! That took care of it!