If your website is not displayed correctly in mobile version, please check the following options:
The default Jimdo mobile version ( design> mobile view ) in custom layout should be deactivated as shown in screenshot:
In Settings> Edit Head section you should have 3 links. Please make sure you haven't deleted them:
<meta name="viewport" content="width=device-width, initial-scale=1"/>
<link href='https://fonts.googleapis.com/css?family=Barlow:300,400,500,600,700,800' rel='stylesheet' type='text/css'>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css"/>
Important!
The viewport tag and font awesome link in new Matrix themes can be found directly in HTML. This has been made in order to avoid mistakes in Edit Head section
If your website is not responsive, you might have made an error in CSS. In this case you need to replace the original CSS files