Well there could be two things:

Firstly I just saw your flash output; can you do a full rootfs+emmc flash since you got it used and don't have much to lose...


Secondly, if after the above fails to fix your issue its possible your screen is damaged hence the issues...Maybe that's why the seller sold it


Anyway, if its a hardware issue then Nokia Care is your solution and no matter which phone; if there is a hardware problem all are crap