You created full width static block https://www.deinfitnessfreund.de/staticblocks/warenkorb-ueber-dem-footer/ and added that to the cart widget area that displays in the column https://prnt.sc/1t8w6wr
So, block from that column displays over the products at the left side. If you want to show any content below the cart form then add the static block below the cart shortcode on the cart page instead of the cart widget sidebar.
Check now.
