Mail opens in the background instead of the foreground.

Hello, on my M1 MacBook Pro, when I'm using, let say Safari, and I want to open Mail, it opens Mail in the background if I'm using Safari fullscreen. So it slides the Safari screen to the left and then I have to click Mail again and it comes sliding in from the left. I really don't remember actively changing a setting. So a little hint maybe would be much appreciated. Grtz. Jos.