Hello, @Kazi Sabit,
Thanks for using our Theme and for contacting us.
In order to place 3 buttons in a row on a desktop, simply go to the Dashboard >> XStore >> Theme OPtions >> Theme Custom CSS >> Global and paste the below code at the bottom of the CSS box there.
.single-product-builder form.cart{flex-wrap:initial !important;display:flex !important;flex-direction:row !important;}
Then save settings and check back to your site after clearing the browser cache. The result will appear like this: https://postimg.cc/kD8z57nz
For the mobile and sticky bar, please share your site wp-admin URL and access in the private content area of this topic by following the below-given format
WORDPRESS ADMIN URL:
WORDPRESS ADMIN USERNAME:
WORDPRESS ADMIN PASSWORD:
So that I will check and fix your issue on your site.
Note: Please take a complete backup of your site first and allow us to debug your site and change/remove the plugins to solve your issues.
Regards 8Themes Team.