got an s21 for free (with lines) is it worth fixing? my main rn is a56.

My sis gave me her old s21, its beaten up pretty much and shes told me to sell it, im not sure if someone is still willing to get this, should i just fix it and make it my secondary? an amoled screen cost around 75 usd and a battery cost like 8 usd. a hundred bucks in total with repair fees included