Quote Originally Posted by impulse View Post
I do not know what this is about.
What exactly confuses you in my explanation?

Quote Originally Posted by impulse View Post
It was difficult to translate some parts of the verses : Некоторые части стихов было трудно переводить. If I am not mistaken that this one is right?
Yep!

Quote Originally Posted by impulse View Post
Some parts of the verses were difficult to translate (for translation) : Некоторые части стихов были трудны для перевода: Here I do not understand how трудны is formed up. Is that somekind of adjective form used to refer to the genitive case?
Full form - трудный (masc.), трудная (fem.), трудное (neut.), трудные (plural).
Short from - труден (masc.), трудна (fem.), трудно (neut.), трудны (plural) - here you need plural because "некоторые части" are in plural.
We usually use short forms of adjectives in the predicate position (i.e.: they are difficult for translation - они трудны для перевода). And it has nothing to do with genitive, since the short forms do not decline at all. They never precede a noun. Another possible gap in your grammar - full and short adjectival forms.

More examples:
Этот рассказ труден для перевода.
Эта книга трудна для перевода.
Это стихотворение трудно для перевода.
Эти рассказы (книги, стихотворения) трудны для перевода.