지금 정신이 없다 means "I'm extremely busy right now" (so busy that I lost my mind) 답장이 느려도 이해 부탁드려요 Therefore, I'm asking for understanding for the delayed reply. Actually, his/her Korean is quite bad. It should have been : "지금 바빠서 정신이 없으니 혹시 답장이 늦어져도 양해 바랍니다" 느리다: to be slow 늦어지다: to be delayed, 이해: understanding (factual) 양해: understanding (emotional), excuse

I think something like, my head is not with it right now so replying will be slow, even so please understand. I'm not that good in korean so don't quote me on that but I think that's what it's saying.