I selected text for the homepage with Studio, but the text is moved to the right side and not to the left where it should be. It appears that it's like on the desktop version where the navigation is left and the text is on the right side. And now I struggle by not finding the CSS-Id on the CSS page to change it. Please help.
The CSS view contains the basic css for the mobile view. The studio is also pulling in your css hosting on your website. In this case, you will need to override some css for the mobile view.
From what I can see, your #Inhalt div contains some inline styles. Then on the CSS view, you may add the following to override the website css.
position: static !important;
width: auto !important;
height: auto !important;
I hope this helps.