is this an american car, or german rather?

Maybe a 1925 Buick? The rear axle doesn't match, but everything else looks close.

Roughly around the 1920ies yes, that is a probable dating range. After taking a second look at the 1925 Buick 2-door Sedan, yes it's pretty darn close.  Do the nr. of rivets on the wheel tell something, or are the wheels arbitrarily mounted independent of the car model?

What about this Chevy 1925 Superior K?

However, I spotted this detail, that looks like a socket, what is it? It seems to be pretty peculiar and may help with the idenfitication? Both the Buick and the Chevy don't have that.

No further clues?

Are you still with me?

Move your post to the “ what is it” category. You’ll have way more views there.