Sorry you are facing this issue, it would be my pleasure to help you.
Welcome to the Shopify community! 
Thanks for your good question.
Please share your site URL,
I will check out the issue and provide you a solution here.
Hi @Atlanticmorning
This is PageFly - Advanced Page Builder. I would love to give you some recommendations
-Go to Online Store->Theme->Edit code
-Asset->base.css paste the below code at the bottom of the file.
@media(max-width:767px){
header{
background: #f8f8f8 !important;
}
}
You can use different color
Hope my solution works perfectly for you!
Best Regards;
PageFly
Thanks for the welcoming and also really appreciate your help!
Hereby the site URL: https://amrhstudio.com
the password is just sent to your email : bamaniyaketan.sky@gmail.com
Thanks for your time.
Ameerah
Hello Pagefly, Thanks for your help. I just add your advice solution, but there still no changes the Header still no overlay on Product page on (Mobile version). Hereby the screenshot on Edit Code with the code placed and saved on bottom file.
best regards,
Ameerah
Can your share for me password or you can send it by email [email removed]
Yes just sent to your email.
sorry reply late. you can add code
@media (max-width:767px){
section[data-section-type=“header”]{
position:absolute !important;
top:0;
left:0;
right:0
}
section[data-section-type=“header”] header{
background:transparent !important
}
}
at the file theme.min.css
Hello Pagefly team! Thanks for your valuable help! Really appreciate the time you made to help me. I really recommend your advice. Thanks a lot. You are the best
You are welcome, I am glad when can help you 
