Hotbed max temp error with new thermistor

Need Ender3 help (desparate)

I ordered the Ender3 in 2022 and on the very first day it destroyed itself by locking its board and just bluescreening. It was no longer functional with the old board so I tried to have it fixed, but nothing worked. I finally ordered a new main board this year and it still wont work. No matter what software combination I put on it it just wont work(yes the sd card has the correct format in case you´re gonna ask) It turns on now but will start screeching after 2 minutes and then freeze.
I had to replace the extruder as that was broken somehow and that works now and then the thermistor broke and I replaced it. But I still get the bed max temp error. No screws are on too tight, the thermistor is brand new, not bent, not broken, plugged in correctly. The firmware is the original (and hopefully right) stuff directly from creality as it is a brand new board. If I do need different software I would love to know what exactly I need as I am a literal beginner and was told that the Ender3 was FOR BEGINNNERS. Talk to me like I’m 5 and don’t use confusing jargon… I literally won’t understand you…
I wanted to use this for my work and I’m about to throw it at my wall and just eat the 300+ bucks I have spent on it if I can’t get it to work and just give up.
PLEASE HELP ME