I need to study English so I can pursue other opportunities in my workplace.
If I study English I may have the opportunity to work in a different department at my work.
"I need to study English.." When you talk about the need to study English or the need to do something it means that you are doing it because it is required or it will bring other opportunities your way.
"If I study....." When you use this phrase you know that "if" you do something it could bring a possibility of something happening in the future. This means you want to take the chance to do this so the possibility of something good can happen in the future.
"I need to study English.."（英語を勉強しないといけない）
"need to" は、義務として、あるいは可能性を広げるために、あることをするという意味です。
"If I study....."（.....勉強すれば）
このフレーズは、英語を勉強することで新たな可能性が生まれることを表します。ここでは、その可能性が実現するように英語を学びたいと伝えています。
I need English to improve my marketability in the workplace
There's a possibility of my transferring to a department where English skills are valued
It depends how much information you wish to share about this topic how much you say. You could respond very briefly:
"I need English for my work," or give a much longer explanation detailing your hope that someone within your company will one day put your name forward for transferring to a department within the company where English may be needed.
この話題についてどのくらいの情報を共有したいかによって異なりますが、次のように非常に簡単に答えることができます： "I need English for my work"
あるいは、あなたの会社の人にいつか、英語が必要な会社の部署にあなたを推薦してもらえるよう詳細を説明してもよいでしょう。
I study English as I am being transferred to a department which requires me to use English
I might be transferred to a department where I am required to use English
I need English as I might be transferred for my work
When you are moved from one department to another then this is called 'transferred' If you can read/write and speak English in your work this is also called 'using' or to 'use' English
"It is possible I will be transferred to a job where I would need to use English"
"I will possbily need high level English skills for a job"
In order to explain that the reasoning behind learning English is the possibility of a new job that requires using English, you could say, "It is possible I will be transferred to a job where I would need to use English". This sentence highlights the reasons for wanting to learn English.
新しい仕事で英語が必要になるかもしれないので英語を勉強していると伝えたいなら、次のように言えます。
"It is possible I will be transferred to a job where I would need to use English"
（英語を必要とする仕事に異動になる可能性があります）
この文は、英語を勉強する理由を強調します。
I study English because I might be transferred to a department that requires me to use English.
I am studying English because I might be transferred to a department that requires me to use English.
I study English' and 'I am studying English' are both the same and both grammatically correct. We then use 'because' before we are going to give the reason. We could also use 'might' or 'may' in this sentence, to show that the reason is a possibility but it is not certain. Then using 'transferred to a department' means that within your company you are being moved to a different job but still in that company. And finally, 'that requires me to use English' you could also say ' that I will need to use English for' in more simple English.
I study English' と 'I am studying English' はどちらも同じ意味で、文法的に正しいです。その後、理由を伝える前に 'because' を使います。また、この文では 'might' あるいは 'may' を使うことができます、これはその理由が可能性であって確定していることではないことを表します。
'transferred to a department' は同じ会社の別の部署に移ることいいます。
そして最後の 'that requires me to use English'（英語を使わなければならない...）は、より易しい英語を使って 'that I will need to use English for' と言うこともできます。
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