Is this your book
これ は あなた の きょかうしょ ですか
book では「 本」です しかし text-book では（教科書）きょかうしょ です text book も 「テキスト本」です
きょかうしょ can't be used to translate book と思っている.
Be careful with the condensed つs. Your ざうし might possibly read as a " seat/place cow," but it doesn't read as "magazine," which has a no う and a condensed tsu (つ), thus: ざっし. romaji=zasshi.
Whose motorycles is that over there?
あれ は だれ の オートバイ ですか？
I THINK that should be either「あれ は だれ の オートバイ か」or 「あの オートバイ は だれ の か」but I can't see any reason why yours wouldn't work.
Who’s umbrella is this
それ は だれ の かさ ですか？
"This" requires a 「この」or 「これ」- same patterns as for the previous question.
これ の やまださん ですか。
Regardless of whether this is expected to answer "Whose umbrella is this?" or "whose motorcycle is that"「これ」needs to be changed to 「それ」
The umbrella is near to or in the questioner's hand, as shown by "this" /「これ」and therefore closer to the first speaker. The motorcycle is at a distance from both people (over there/yonder/yon), but once it has been mentioned, it becomes a subject at a short remove, so the "not-too-far-off there" is needed to answer.
To remain as close as possible to your structure, 「それ は やまださん の です」, しかし, 「やまださんの」would be the natural language response. This is a statement, not a question: か functions as a question mark.
そうですか。same as above for the か here. I would expect to hear something more along the lines of 「そうですね」in a polite setting, or 「そうだね」and even「そうだな」in an informal setting