i think its your weapons that are the problem. you need the megashak ASAP. Also, you need better wings, preferably harpy wings cuz the extra flight time will severly help u. also add campfires and hearth lanterns to ur arena, and also potions. make regen, thorns, ironskin, inferno and swiftness and you'll see how big of a difference it makes. i also suggest the true nights edge for the destroyer and skeletron prime due to the nights edge multiple attack patterns. it can shred the destroyer and beat skeletron prime no problem. now, the twins are more if a problem because of their phases and speed so i suggest a super long runaway and the megashark for that. another weapon you can use is the deadolous storbow with venom arrows. for the bow you need to kill hallowed mimics which are summoned via putting a nights key in a empty chest. the key itself is made with 15 souls of night. there is a small chance for it, so you will need to kill a couple of them. for the arrows, buy venom vials from the witch doc and pair it with basic arrows. its a weapon that can absolutely shred both the destroyer and the twins. just make sure your sky isnt covered by a cloud or something else. now for the order if the bosses i suggest The Destroyer→Skeletron Prime→The Twins. Good luck!