Image to flip

first of all – your link does not work.

next on those alb elements ( grid-row and the cell that has the flip-box) set all paddings to zero. If you do not set – there will be default ones set by enfold.
Do not set min-height for those! – i used for grid-item that option : Inverse Layout – Ignored For Tooltip

give a custom class to the grid-row – i tested it with my setting : one-flipper

synchonize the break-point at media-query to the grid-row breakpoint.
i have set 767px but if you like you can do it with 989px

@media only screen and (min-width:768px)  {
  .av-layout-grid-container.one-flipper {
    min-height: 28.12vw;
  }
  .av-layout-grid-container.one-flipper .avia-icon-grid-container,
  .av-layout-grid-container.one-flipper .article-icon-entry {
    min-height: 28.12vw;
  }
}

@media only screen and (max-width:767px)  {
  .av-layout-grid-container.one-flipper .avia-icon-grid-container,
  .av-layout-grid-container.one-flipper .article-icon-entry {
    min-height: 56.25vw;
  }
}

now for understanding: your image has a 16/9 ratio because the image is set to cover the background hat to be of that aspect ratio.
the screenwidth is 100vw – and the height than must be in a 32/9 ratio ( because only the half container should be 16/9)
9/32 = 28.125
the whole grid-row now has to be 28.125vw in height !

Sample Page: https://webers-testseite.de/isp/
and css for normal flip

i see that you have set on the page /our-clinic/about for the other cell a min-height – that will be possible if you want only the flip-background image to cover only ( including crop ) – you have to remove all paddings on that cell with the flip-box and set the same min-height / height option there !!!
my method above is only to have totaly responsive bg-image for flip

you can test if for the above page by:

.av-layout-grid-container.av-li73q-e1db10c26939acc99331ee70921182c6 .avia-icongrid-flipbox .av-icon-cell-item .avia-icongrid-flipback,
.av-layout-grid-container.av-li73q-e1db10c26939acc99331ee70921182c6 .avia-icongrid-flipbox .av-icon-cell-item .avia-icongrid-front {
  margin: 0 !important;
}

.av-layout-grid-container.av-li73q-e1db10c26939acc99331ee70921182c6 {
  min-height: 500px !important;
}

.av-layout-grid-container.av-li73q-e1db10c26939acc99331ee70921182c6 .avia-icon-grid-container,
.av-layout-grid-container.av-li73q-e1db10c26939acc99331ee70921182c6 .article-icon-entry {
  min-height: 500px !important;
}

.responsive #top #wrap_all .flex_cell.av-5cyqiu-1b136132ec762676c6173331de16be40{
  padding: 0 !important;
}

i would give the grid-row a custom class or ID and set the css for that.