Why can't I say "Jsem děvče nebo kluk?". Duo didn't accept it.
You can, it is accepted. Use "My answer should have been accepted" and might be able to tell you more.
It's saying I should have put jsem holka čí kluk, presumably the čí is wrong?
či / nebo = or
čí = whose
I put "Jsem divka ani kluk" and it counted it wrong, correcting the "ani" to "či", which wasn't listed in the translations for "or". Sorry to be picky, I just thought that it should be noted.
"či" and "nebo" are synonyms, so either can be used.
His point was that one of the translations shown for "or" is "ani", which was corrected to "či", which isn't shown in the translations.
Yes, that can happen at any time if Dolingo decides to show alternative translations instead of the main one. It is pretty unpredictable at that.
could someone explain, why "Jsem holkou?" (accusative) was correct but here you have to say "Jsem divka...? (instrumental) I mean not the words, but their cases..Just can not get it.
"Holkou" is an instrumental, "dívka" is a nominative. You can use either of the two, if it's not included in the translation then it's been most likely overlooked, report it then using the button.
Whats the difference in kluk and chlapec?
"chlapec" is more formal, "kluk" is more informal and more commonly used in speech
How do you know when to use kluck, chlapec, or hoch?
Please see the link in the answer to Zie.