Cant turn brightness up

I have a Samsung Galaxy a20e and its pretty new and i havent used it. I was going to have it switched over to my current plan , but when i turned it on the screen kept freezing up and a lot of static(?) Started appearing on the screen. I didnt know what to do for a while. I mean the screen was froze but i can still hear apps being clicked in the background when i tapped on it in random places where the apps would be. I pulled down the settings tab which was the easiest thing to do , though i couldn't see the settings because my phone was froze on the lockscreen. So i lowered my brightness and my screen kind of unfroze but now i have to keep the brightness on low because if i turn it up even slightly the screen glitches and freezes again. This doesnt exactly solve the problem and i now have 3 slightly visible lines on my screen.

Please help! I really dont know what to do now!