Does Kassen fyldes med glas describe the act of filling a box with glass or a box that already contains glass?
It describes the action. Der Kasten wird mit Glas gefüllt.
Ah ja, danke! So a less ambiguous translation of the Danish sentence would be "The box is being filled with glass." And when I want to describe the state of a box that is already filled: "Kassen er fyldt med glas".
I'd go so far as to say that "being" is missing in the word bank.
Yes. I once edited an important document written in English by a Dane. It was filled with 'is done' sort of constructions, which should have been active: do.
This is about the MOST useless Danish sentence EVER!!!
The correct translation would be: "The box is being filled with glass". "The box is filled with glass" would be: Kassen er fyldt med glas".