Why do I always have this overlay when I start my laptop?
Since probably your home changed. Change the times again to Google.
How do you do that?
You probably installed a program which also changed your homepage in Firefox.
The message itself is nothing extraordinary, you get on almost every page, only more or less verbose. Sometimes it's just a banner overlay up or down. Is actually so prescribed since the new data protection law, and since almost every page uses Google Analytics you have to stop or forbid…
If I were you, I would click on the Citizen Menu in the top right corner of Firefox (3 dashes on top of each other), then change your start page under Settings. Best on standard, blank page or whatever you want. Afterwards you can change your default search engine back to Google in the settings under the item search.
Then you should change your start page