How to properly brine and defrost 20 pound turkey?

I'm cooking turkey on my own for the first time. I've never even seen someone cook a turkey. I'm so stressed. If i dont get this right my family's thanksgiving dinner is ruined. I don't know who to defrost a turkey, I need it to defrost fast b/c thanksgiving is in two days, I don't have enough time to defrost it in the refridgerator. Also, can i put the turkey back in the fridge once its fully defrosted and cook it when i'm ready? or do i have to cook it right after its done defrosting. Also, are we suppose to defrost a turkey thats already thawed? or frozen and brine it while its defrosting. Please help, if your confused I'll edit this to answer your question so you can help me thanks guys!!!!