RE: RTX 3090 with low performance
Did you buy it brand new or from a reseller who previously used it for cryptocurrency mining? If it's the latter, the card would have been under tremendous stress and it wouldn't perfect the same as a new one.
Anyway, what game were you playing?
You might need to upgrade other parts of your computer for better cooling. The RTX 3090 uses more power so you're going to need better cooling. Stuff like a better case with better airflow, more fans, water cooling, etc.
I would also try to adjust settings and check RAM.
