How much would it cost to fix the back end of a Toyota camry 2018 hybr

@usmanq really not a whole lot. There are way to many variables to get you anything exact or even close since we do not know the extend of the damage. First off start by telling us where you are located (Country only) so we have an idea about cost and availability of replacement parts. NExt we would need to at least see the damage. Post some good pictures with your QUESTION (EDIT that one) by using this guide iFixitでの質問に画像を追加する方法

Further down the line you need to consider that may require a frame straightening service to check your body frame and subframe etc. As you can see there are lots of things going on and these are just the beginning. This might by a good exercise but ultimately you must still consider whatever answer you get on here, to be a guess. There are reasons why insurance companies write some of those off pretty quick It may be a total loss.