The logo containers (.container-erfahr ul li) are currently set to float left in their CSS. Due to the second one being taller than the third, the fourth is displayed below the third (and to the right of the second) in mobile view - as per the behavior of floats.
To rectify this and center them instead, remove the float: left and change them all to display: inline-block. For centering, add text-align: center to the container element .container-erfahr.
Here are the updated rules:
.container-erfahr ul li {
display: inline-block;
margin: 30px;
padding: 0px;
border: 0px solid lightgray;
list-style: none;
}
.container-erfahr {
margin-top: 100px;
margin-left: 0px;
text-align: center;
}