It may be a long time before I get the spelling right on this one
Hahaha I wrote "orangkolora"... it's orangxkolora (note the gx) in Esperanto xD
In many cases adjectives go after nouns. Why To jest ryba pomarańczowa is incorrect?
Because that would mean something like "this is a fish made of oranges". Please read "The Meaningful Position of Adjective".
Yes. The particle "to" replaces the verb "jest". You may like to read this thread .