YOU SAID:

i know you're very busy, so i won't make this too long

INTO JAPANESE

あなたがとても忙しいことはわかっていますので、あまり長くはしません

BACK INTO ENGLISH

I know you are very busy so I won't make it too long

INTO JAPANESE

とても忙しいと思いますので、あまり長くはしません

BACK INTO ENGLISH

I'm sure you're very busy, so I won't make it too long.

INTO JAPANESE

とてもお忙しいと思いますので、あまり長くはしません。

BACK INTO ENGLISH

I know you are very busy, so I won't make it too long.

INTO JAPANESE

大変お忙しいとは思いますので、あまり長くはしません。

BACK INTO ENGLISH

I know you are very busy, so I won't make it too long.