Why my iPhone notch right side is having horizontal green lines

Hi guys I really need help if someone can tell me how to fix these green lines on right corner of my iphone notch .

Let me explain how these lines appeared in detail

I bought this iphone from a guy he said that the face id was not working after the update i thought it was ios buy

Gladly when i factory reset my iphone face id started working properly i was like dang man i got luck !!!

After a while I realised its earpiece speaker was not working then i took my iphone to a local repair shop and they replaced the speaker with other one and the moment I entered my house and showed my iphone to mom in front of her suddenly screen started flickering like a ghost took possessed it !!

Both me and my mother was in shock what happened just now !

After screen flickering the green lines appeared on my iphone’s right side of notch and those were horizontal

Those green lines were increasing and decreasing just my inc or dec brightness of screen

I took it to apple care they told me screen needs replacement

Can anyone help me out what’s the issue !! 🥲