도움이 되지 못해서 미안해를 영어로?!
In my case, my client assigned me to manage his case. But unfortunately, I don't have time to deal with. So I would like to say "도와주지 못해서 미안해" in English
Please help me! Thank you.
To be polite, you can say 'I would love to help you with (*), but due to a heavy workload and prior commitments, it is best if (name) can assist you instead.'
And CC that person on the email, so the client sees that you want to help, but can't.