How to REMOVE DROP SHADOW from Testimonial Slider Header

Site URL: https://www.theplatinumplan.com/

Hi, 

I'm creating one of the DIY Testimonial Sliders but a drop shadow plugin I used for the Header is also being displayed at the top of the Summary Box showcasing the testimonial. Is there any way to constrain the drop shadow to just the top navigation header only?

- First testimonial is in a Text Box, Second is in a Summary Box
- PW for site is wompwomp

In Custom CSS, find this code

Header {
    box-shadow: 0px 3px 15px rgb(100 100 100 / 29%);
    -moz-box-shadow: 0px 3px 15px rgba(100,100,100,.29);
    -webkit-box-shadow: 0px 3px 15px rgb(100 100 100 / 29%);
    position: relative;
    z-index: 4;
}

change Header to header#header

@tuanphan 

Hi, and thanks for helping. I tried the code change but it removed both header shadows rather than JUST the one over the Summary Box. It also caused the nav header to scroll up rather than remain fixed.

Is there something else I should try?