Hi, Shane is unavailable this week so I'm checking on his outstanding tickets. I hope that's okay with you. I was able to see the custom search filters when testing in Safari, and I can see the issue. The problem is that some of the search filters are included in divs that are set to "float:left;" using CSS, as you can see in the screenshots here. Since these elements are floated, the parent element, #suche-rahmen, does not wrap around those floated elements. The solution could be to remove the float:left from those child elements #suchhaelfte1 and #suchhaelfte2, but I'm not sure how that would change the design of your site. That might not be appropriate. If you cannot remove the floats, you could add another div element below the two floated child divs with CSS like "float:clear;" to force the border of the parent element to extend around those floated elements. So the solution depends on what you want to accomplish with floating the two child elements, I can't say based on the information I have available.
Yes, when I first visited the site in Google Chrome on a Mac, I was redirected to some ad or junk site. When I visited the site again in Safari on a Mac, I did not experience the same issue.
It may also be related to whether you load the site with or without www. in the URL, I can't tell, and I'm hesitant to visit it again in Chrome since it seems a little sketchy.