Responsive page, CSS grid, Bootstrap

Hi everyone. I look forward to your feedback. How do you make perfect border-radius curves? Do you have to surround the element with a div and apply the border-radius to that div? I had to use bootstrap for the "proceed to pay" button because the border-radius was looking weird. If you look at the box around the price-plan, you may notice the difference in border-radius outlook, compared with the button.