The motherboard is fine, unless you want some of the overclocking features there’s really no need to go above the b550 chipset for a Ryzen 5xxxx series.
That CPU will be excellent paired with a 3090.
You will need more RAM. At least 16GB in a dual channel kit, though 32GB would be better. Going beyond that would be kind of pointless at this point.
The PSU you would definitely need to upgrade. You’d need a minimum of 750W, but going with a 1000W PSU would give you some headroom for future upgrades for a pretty minimal price increase.