Changing Items in Carousel automatically from 2, 3 or 4 to 1 on mobile

Hello,
I*m using AT Team Section and AT Posts Column.
Whith a big screen, it looks good. But on mobile, there is no break, so the text splits and it doesn’t look good. How can I create by css, that mobile desktops only show one item (instead of for example 3 or 4)?
The Site is https://bkhev.de
Actually, you see the problem only at at-team.
I would also like to change the posts from one to 3 or 4 Items for the big screens. But actually, changing to one item doesn’t work on little screens.
I hope, you understand my question.
Thank you for your help.
Best regards
Heidrun