Hides slides – except the middle one plus 1 left and 1 right

Hello Web Heros, I am struggling with the following problem: I have a carousel slider (please scroll down to the glasses, not the hero slider), everything works fine, but my client wants exactly 3 slides visible in the viewport. The middle one, one on the right and one on the left (disabling all the others, that are visible at the edges) . Does anyone have an idea how to solve this? Please click 2, 3 times on the right arrow to get to the initial position of the slider (the slider jumps to slide 2 in the published site to show an element on the left).
Thank you very much for your help, appreciated!

IMPORTANT: Please exit preview mode and enter again, otherwise the slider is not working (for some reason!)

Here is my site Read-Only: