Howto enlarge image "geodir_thumbnail" within "gd-bubble"

Sorry, again me, but i tried this for hours now.

I would like to enlarge the whole geodir_thumbnail on the homepage, but i fail…

i tried to hardcode i.e.

geodir-bubble_image .geodir_thumbnail
{padding: 0px;
float: left;
width: 100px;
background-position: 50% 50%;
background-repeat: no-repeat;
background-size: cover;
position: absolute;
top: 0;
bottom: 0;
left: 0;
right: 0;
margin: 0%;
width: 400px !important;
}

in combination with:

.gm-style-iw
{width: width: 400px !important;}

i have check the forum in and out (https://wpgeodirectory.com/support/topic/thumbnail/, https://wpgeodirectory.com/support/topic/map-pop-up/ and many more) and it looks like this could me a google maps issue, still it would be great if you could answer if the effort is lost or how i could enlarge the image to let’s say i.e. 350x350px…

Thank You and sorry for another annoying and problem already 50x answered issue (but i can’t find the solution in the forums, nor via google)…
Cheers,
Benjamin