Black Multi Print Curve Tracksuit

Hello can you please let me know if these run small or big. Do we need to size up or down. I wear a size 18 so what size will I have to order and do it stretch.

I emailed as soon as I got it asking about return for another size and no one ever responded

I picked the size I wear and when I received it it would go pass my Thighs I was am so angry about this