Hello, @Recep,
When I checked your site, the mobile sticky add-to-cart button is not appearing on the product page you can check here: https://streamable.com/avucme
The option of the sticky add to cart is already disabled when I check your site see image: https://postimg.cc/HjhX14dP
To change the color of the button simply go to the Dashboard >> XStore >> Theme Options >> Theme Custom CSS >> Global then paste the below code at the bottom of the CSS box.
.single_add_to_cart_button.button{background: red !important;}
Then save settings and check back to your site after clearing the browser cache.
Note: In the above code the word “red” is the color you can change it as per your requirements.
Regards 8Themes Team.