Hello @morad,
1. In order to solve your issue, please copy and paste the following CSS code to XStore >> Theme Options >> Theme Custom CSS >> Global CSS and then clear your browser cache to check the results.
@media(max-width: 767px){
.single-product .page-heading {
margin-bottom: 0 !important;
}
}
2. Do you wish to make the “Add to Cart” button full width to the complete row on the mobile version?
Best Regards,
8Theme’s Team