He's right about the odd-height of top and bottom steps. Usually, new steps are framed AROUND the existing concrete steps as if they aren't there. If you don't have the room to make your steps at least 6" wider on each side, then you may need to remove the concrete steps (in the name of 'saving space'.)
As the Man already said, there are many ways to do this project. My best to ya and hope this helps.
Jay J -Moderator
PS: It's hard to see what 'concrete answer' (not to coin a pun) there is for you because I/we can't see the steps from here ...