How to increase author image size in testimonial extended?

To increase the feature image in Divi Testimonial Extended please add the following CSS in Divi Theme Options.

.el-testimonial-portrait {
    width: 135px;
    height: 135px;
}

.el-testimonial-portrait img {
    width: 135px;
    height: 135px;
}

Change the width and height values as per your requirements.

Output: