How to exit the Windows S mode?

Leaving Windows S mode is final and a return is thus impossible.

Exit Windows 10 S mode

1. Open the Windows 10 settings, which you can access via the Start button and the gear icon, among other things. Navigate to "Update & Security" and there to "Activation". 
2. In the "Switch to Windows 10 Home" or "Switch to Windows 10 Pro" section, click "Go to Store". If there is an "Upgrade your version of Windows" section, be sure not to select "Go to Store" at this point.
3. In the Microsoft Store, you can now exit Windows S Mode via the "Get" button on the "Turn off S Mode" page, which is partially named somewhat differently. 

Windows 11 Modus verlassen

1. Open the Windows 11 settings and navigate there via "System" to "Activation". 
2. Select the "S mode" subitem. After unfolding, the "Open Store" button can be pressed. 
3. By default, the correct page opens, where the "Download" button can be used to exit Windows S Mode. It may be necessary to manually navigate to the "Turn off S Mode" page or similar and click "Retrieve" there.

You can find more information, for example the advantages and disadvantages of the S mode, here: Windows S Modus - Alle wichtigen Informationen im Überblick