Magic Mouse 2 lag - trackpad reacts strange

Since I upgraded to Big Sur, I have severe issues with my Magic Mouse 2 (lag) and the track pad shows, although less, a strange behaviour (suddenly zooms out). I know my Mac is not recent ( MacBook Pro (Retina, 15-inch, Mid 2015)) but nevertheless I did not expect that problem.

The problem with the mouse started already on Catalina and I hoped it would be resolved with Big Sur. But not.... Any advise ??? And as I'm only using an Apple Mouse, not keyboard... Apple should resolve the issue, correct ?