Will not start?

I’ve had charging issues in the past. I turned my car off one day, went to turn it back on my battery light came one went to O'Reilly's got a new battery but it in, battery light still was on tested alternator, said alternator wasn’t working (mind you my car still starts). So, I found a guy to replace my alternator. When he went to start to replace my alternator he disconnected the positive cable to my fuse box underneath my hood, then as he was disconnecting the positive cable at the back of the alternator by the pig tail there was a few sparks flown so we got the new alternator on and my car started but immediately shut itself back off, it felt equivalent to running out of gas, like the car just ran out of power. Then my warning lights started flickering the eventually everything went dark on my dashboard. However, all my regular dash lights illuminate when I lock and unlock my car it just won’t start now (mind you it started with the old alternator). Someone please help.