A concert

Could you correct my writing below.

When (change to "While I was having..") I was having curry rice at a restaurant, I answered my friend's phone.The content of the call was her invitation to go to a concert (I would say "She called to invite me to a concert).  It is a duo singer in South Korea .  One of them sings well and his voice attractives audience (his voice is amazing, and he always has a large audience).
This event will be held in Hiroshima in the middle of October.The concert will be over ("the concert will end at..." is a little better, but your phrase is fine)  around at 10 pm so I will not be able to return home the same day.I will have to stay at a hotel one night so I will ask my boss tomorrow to allow me to (your phrase is fine but I would say "...to let me take a day off..") take a day off. I hope that I will ("I hope I can...") go to the concert.

A concert

Could you correct my writing below.

When I was having curry rice at a restaurant, I answered my friend's phone. The content of the call was her invitation to go to a concert. It is a singing duo in from South Korea. One of them sings well and his voice is attractive to the audience.
This event will be held in Hiroshima in the middle of October. The concert will be over around at 10 pm so I will not be able to return home the same day. I will have to stay at a hotel one night, so I will ask my boss tomorrow to allow me to take a day off. I hope that I will go to the concert.

editor note: This was really good. Remember to put spaces after periods at the end of sentences. I changed "attractives" to "is attractive to". I changed "duo singer" to "singing duo". I struck out a couple words you don't need.