dead?

i think my graphics card is dead, i just got a Gigabyte eagle geforce rtx 3090 and was running well for a month or 2. a couple of days ago i turned on my pc and was doing schoolwork, no streams or anything opened up, and it just black screens but my PC fans and rgb was still on. i powered it off...

I just got an opened box Rx 5700xt Red Devil from Microcenter. After I put it in, the fans spinned for 3s and stopped, no light at all, then pc constantly crashed cause overheating. I used a 8pin to two 6+2 pins with corsair mx 1000 Psu. Could it be because of the conflicting old driver (was...