ご質問ありがとうございます。
「"What is your dream in the future and why?"」は大体良いですが、私の意見で「in」の代わりに「for」のほうが良いと思います。なぜかというと、「in the future」の場合は「[夢](https://eikaiwa.dmm.com/uknow/questions/52182/)は[将来](https://eikaiwa.dmm.com/uknow/questions/36959/)にある」というニュアンスがありますから。「for」を使うと、未だ叶っていない現在の夢というニュアンスがあります。
日本語と同じく、二つの英文を分けたほうが良いと思います。
＜ボキャブラリー＞
dream = 夢
future = 将来
dream for the future = 将来の夢
ご参考になれば幸いです。
In order to find out what a persons dream is for their future and why this is there dream, you can ask "What do you want for your future and why?". This question is very specific, it asks what they want, but also asks why they want this. This gives you a detailed answer to your question.
人に[将来の夢](https://eikaiwa.dmm.com/uknow/questions/4812/)とその[理由](https://eikaiwa.dmm.com/uknow/questions/51867/)を尋ねたいなら、次のように言えます。
"What do you want for your future and why?"
（将来の夢とその理由を教えてください）
これは非常に明確な質問です。将来の夢とその理由を尋ねています。このように尋ねると、相手は詳細に答えてくれます。
If you have a plan and really want to do somehing in the future then this is call a 'dream' or a 'goal'
the future is the time that is coming up ( not now) by asking why this gets them to explain why they want to do that thing
将来実現したいと強く望んでいることがあるなら、それは 'dream' または 'goal' で表せます。
'the future' は、（現在でなく）これから先の時間を指します。
'why' と尋ねることで、それをしたい理由を確認できます。
Tell me what your dream for the future is and why you have chosen that dream.
What's your future goal and why are you aiming for it?
What would you like to achieve the most and give me the reason why?
Most people, especially the young and ambitious, have dreams for the future. Dreams can also be referred to as goals or future achievements. If one does not have a dream, that person does not have a goal or something major that he/she would like to achieve in future. Chasing dreams is what keeps most people hopeful. Every person who is chasing a dream has a reason why he/she is chasing that dream. Those that don't have hope for the future live miserable lives.
So, you may ask a young person as follows:
Tell me what your dream for the future is and why you have chosen that dream.
or
What's your future goal and why are you aiming for it?
or
What would you like to achieve the most and give me the reason why?
ほとんどの人、特に若くて野心的な人は将来の夢（dreams）を持っています。「夢」は 'goals'（目標）や 'future achievements'（将来の成功）と表すこともできます。夢のない人には、目標や将来成し遂げたいことがないということです。
ほとんどの人は夢を持つことによって希望を保っています。
夢のある人には必ずその夢を追う理由があります。将来に希望の持てない人は惨めな人生を送ることになります。
若い人には次のように質問できます。
Tell me what your dream for the future is and why you have chosen that dream.
（将来の夢は何ですか、その理由も教えてください）
What's your future goal and why are you aiming for it?
（将来の夢は何ですか、その理由も教えてください）
What would you like to achieve the most and give me the reason why?
（一番成し遂げたいことは何ですか、その理由も教えてください）
It is great to have goals and aspirations, it gives us the motivation to keep pushing for the life we would like to one day live.
We can use the above sentences to ask someone what they wish for in their future and why they wish for what they do.
goals: the things you would like to achieve in the future
aspiration: the desire to achieve
achieve: to succeed in something
"What are your ambitions for the future and why?"
'Ambitions' is a term used to describe someones goals and dreams, things that people want and want to work towards.
these sentences are asking what are your dreams/goals/things you want to accomplish for yourself in the years to come.
"What are your ambitions for the future and why?"（将来の夢は何ですか？そして、その理由は？）
'Ambitions' は人の目標や夢、望みを表します。
これらの文は、その人の夢／目標／将来達成したいことを尋ねます。
アメリカ合衆国 
イギリス 
南アフリカ 
