I moved into an older home and i am trying to add a GFCI in a kitchen outlet by the sink. Its a two gang box with a switch and one outlet, it has 3 lines coming into the box, two go to the light switch and only one 14/3 wire connecting to the outlet.
On the 14/3 wire going to the outlet both the red and black wires are live. the way it is connected currently the neutral is shared and jumped at the outlet (picture attached).

