Thanks for writing in!
I can see your heading is not responsive, so in a mobile device it pushes the buttons to below and hiding it.
If the heading would responsive and in a mobile device it would be smaller, then the button will get space.
To make the heading responsive please add the following code to the base font setting of your headline element.
calc(1.2vw + 20px)
You can adjust further to make it appear better for your layout.
Then the button, I can see there is left margin in the second button. Please remove left margin and add right margin to the first button and top margin to both the buttons so that it would look better in mobile.
Hope this helps!