Thank you for question and our team is happy to help in any way we can.
It looks like you are seeing this in the GridOne theme due to some of the default styling rules in the theme related to the button-primary and button-secondary CSS classes.
By default those buttons have the display: block; rule applied to them and then at screen sizes larger than 768px (tablets and desktops) it changes to display: inline;. That is why the buttons are stacked on mobile and display side by side everywhere else.
If you wanted to use CSS to change the positioning behavior of those buttons then you could use something like this:
.button-primary,
.button-secondary {
display: inline;
}
That will overwrite the setting for mobile devices and allow those buttons to show as expected. I hope that gibe you the design you are looking for and please let us know if there is anything else that we can do to help.