Text size decrease in responsive mode

Hello ,

I have a problem with my product overview pages on a mobile device. It seems that the tekst of the butons are to big not fit two products on the page and that there is also a red bar on the right sight thus appears as you scroll to the left of the page.

Here you can see my problem: https://www.whalykopen.nl/accessoires/

In addition, the title must also be smaller so it fits on the page from 480px.

Can I do this with custom CSS or somewhere in a child theme ‘functions.php’ ?

Thanks in advance!