Wow – gorgeous site! You can change the values this way to increase delay between slides and also to pause the slider when the user hovers over it to read the testimonial –
[responsive_slider type="testimonials2" animation="slide" control_nav="true" direction_nav="false" pause_on_hover="true" slideshow_speed=8000 animation_speed=600]
Increasing the value of slideshow_speed will help the testimonial stay longer in the user view. Make sure the pause_on_hover value is set to true as well.