I bought this Filzer pump from a used bike shop and the schrader works just fine. When I go to swap it to presta, I am met with this silver head (2nd pic) that won’t press inward— only outward (via pressing the opposing schrader piece, shown in 4th pic).

I am so confused and wonder if I am missing an additional piece?!
There are *zero* demos that properly show the schrader/presta swap on this particular pump (as it’s kind of an odd piece, no?), and *zero* manuals online.

Appreciate the help & sorry if Im actually just an idiot!!