How can I correct my geometry here?

I built a ring and I can’t manage to correct my geometry there. I attached a picture how I want it to be corrected and after that, I will apply some chamferEdge for the render. If the geometry correction is possible like in the picture, how can it be achieved? I’m intermediate with Rhino. Thanks!
Ring: Ringbody.3dm (1.3 MB)

You need to untrim and extend that one surface. Then carefully retrim everything. You can do that with Extend surface (smooth) command.