How do I fix the cable on a weedeater featherlite fl20 it has come unattached at the head. How do I get the nut off the shaft?

I believe it's a reverse screw...

Yes, it is left handed threads I do believe.

I have a troy bilt weedeater split shaft.how do I get the upper cable out of the upper shaft,the head of the spining shaft will not turn