Offset two curves inwards

As the title I just want to offset two curves inwards but I’m struggling. Trying stuff but limited understanding sometimes. Tried creating a surface thinking if I got the perimeter curves it would put them on the same plane to offset inwards. But some go out and some go up :rofl:

so trying to move the red line to the green line. Towards the center of the two curves

for now going to try get the center of the surface. center of the two lines and create a vector between both lines to move could work.

got it sussed with this