Order summary card with Flexbox

If you have some advice to make my code better, for example some CSS tricks to make my CSS less longer, go ahead, I will be happy to receive it !

However, there is always a little problem, when the the viewport width is around 400px and below, the change link is overflowing of my container, how can I fix that ?

I used filter : brightness() for the hover effect on buttons, is it correct ? Or is there better way to do this ?

Did I always need to install the new font-family on my laptop to use it ?

Thank you if you have answered me and have a great day !