Screen with white strips fading in and out, and on and off

My macbook pro took a hit on the side of the screen nothing too significant (so I thought) it left an indentation though.

The day after it started to display white strips that fade in and out on and off. The issue seems to fix it selft after few minute. (Maybe after warming up?? Not sure).

I took it to an apple repair shop when I try to show them the issue of course the laptop didnt show the issue anymore, luckily i took pictures and recorded a video with my phone of the issue so they can see it, as I knew it would be highly likely the issue wouldnt be displayed at the apple repair shop.

The guy at the repair shop told me it was the screen and that it would cost me around 800 euros to get a new one.That was around 3 weeks ago.

Today it showed the issue again. I think, having shut it down completely for a couple of hours somehow triggered the issue again, although that's something i sometimes do, however, today hasnt been as hot as it has been lately.

Anyway i manage to make a gif pic of the issue . although it got fixed few minutes after (around 5 min later).

Can someone tell me whats the actual issue?

And if in fact the only way to resolve it is by spending 800 euros to replace the whole screen?

Thank very much for all the help in advanced!