Not very well explained.
You can get 3 max copystrikes and your channels is gone.
Copystrike expire in 6 months from date when you got it, but if you recieve 2nd during duration of first one, lets say on 4th month you will get +6 months at the end of original duration of 1st copystrike which means 12 months from very first copystrike.
If you are sure that you cant contact claimer and remove your copystrike then it doesnt matter do you keep or remove your video, but at any point you can go and try to apologize and if they are friendly they will remove copystrike.
I already removed the video because i panicked, can I still asked the claimer to remove the copystrike even if i already deleted the video????
Not sure. You would be better off to ask youtube this question directly since you can no longer even see the copyright strike in that section of your YT dashboard. Even though you don't see it in your community guidelines section because you deleted it ... the copyright strike still stands against you, so I believe you should still be able to contact the original complainant and beg for forgiveness. Good luck getting the strike removed. I do know others have had success!