How to invert animation?

I created half of a jump. Next to the frame of the maximum position, I wanted to invert it to make it easier for me to animate. So basically the character needs land back. I’m stuck, I can’t do that. How can I change Time offset to do that, when if I’m changing it - it switching the animation, not adding second half of it. And I want to add the second half to aleady existing part that I created, let’s say from the frame of 46f. Just simple inversion of the animation from the frame 46f, duration of 36f frames, so it would end at 80f. How can I manage my group of layers that way, to do that?