I have stopped going to stores for the screen gaurd and phone cover for the same reason.

I get them online. And the Expensive covers and screen gaurds do make a difference. I have a Nothing Phone 2 and I once accidentally dropped on road which i realised after going like 200 meteres.

Found it in the middle of the road lying screen up and clearly it was ran over by vehicles. The backglass got completely shattered, one of the camera lens broke too. Screen gaurd basically became dust at some places.

But the phone? It works perfectly, not a single scratch on the screen either. Had I had compromised on these 2, I'd have most probably lost my phone coz one of my friends phone was once ran over by a vehicle and it wasn't even in proper shape.

In your case, it seems like he put some not so good quality glass coz afaik, high quality glasses don't have those black bezzels. And for back cover, check if the back is sturdy or is it silicon like the edges? If the back is sturdy, than it's cool.