Hi
Open custom.js file from js folder of your theme directory and go to line no. 112 here you can see the testimonial-slider function so you can just add the speed parameter at the end or after autocontrol.
Ex: `jQuery(window).load(function() {
jQuery(‘.testimonials-slider’).bxSlider({
slideWidth: 990,
minSlides: 1,
maxSlides: 1,
slideMargin: 32,
auto: true,
autoControls: true,
speed: 500
});
});`
Thank You
