Having trouble with Nyx

Her Kangaskhan sweeps my entire team. My Gengar is super effective but it doesnt matter because the Kangaskhan uses Return and since its mega evolved it moves twice so even if I were to equip a focus sash it wouldn’t matter (untested but I assume that’s how it’d work). Can anyone help me out here? The only guides are telling me the type advantages which isn’t very helpful.

Solved it with a choice scarf on my gengar, I’m so happy it worked!