White Background after Sonoma Update

I have a white Background after the Sonoma Update. I have deactivate the Widget Function but the Background is still white. I can change the Background how I want in the Settings, it's still white.

Right click is not possible. It's like that someone cover the original Background. I don't know what to do.

Anyone same Problem ?

Using a Mid 2011 iMac with SSD.

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Edit: Find a Solution. When I deactivate the Background as Wallpaper Function it works but Mouse jerks.