cut my hair, or grow it out?

I need help! 😭 my hair is basically dead, I really want to cut it short to make it a bit more healthier! It is a little above halfway up my back, and when the hairdresser dyed it, she thinned it out and so they're nothing there. I want to make it healthy and thick again, so cut it short, but then again I wanna grow it out 😭 guys what do I do? Cut it short, or grow it long?