Would the antagonist be the Germans and the type of conflict man vs. man? Also, would the climax be when Sini and Rachel move in with the Oostervelds?

Yes. The antagonist is the Germans or Nazis and the conflict is man vs. man.

I haven't read the book, but wouldn't the climax come when the war ends and the girls can leave the upstairs room?

Oh, ok. Thank you very much! I have one more question, what would the theme be?

I can think of several themes -- the Holocaust, survival, growing up. What do you think the theme is?

To determine if the antagonist in a story is the Germans and the type of conflict is man vs. man, and if the climax is when Sini and Rachel move in with the Oostervelds, we need more information about the specific story you are referring to. Could you please provide the title and/or more details about the story?