Hello.
I must be in the nominative case. Not only "to be" is a copula, even "to
become", "to keep being", "to stay something" and "to seem as" are copulas and
are those kinds of verbs where both arguments are in the nominative case. What
is your mother language? For English speakers this might be hard, because there
is hardly no case opposition, but for Germans or other case languages that might
be easier, as they do it intuitively.
Your sentence then is: "...mişşanei unwitans magun şiudanos wisan"
But I'm not sure about the order, whether it must be: şiudanos wisan or wisan
şiudanos. I would say the latter one.
Liubos goleinis.
Kevin