AMD Ryzen especially multi core like yours 12 cores and 24 threads. It will run hot with default setting. unless you tweak a little bit with pbo either eco mode and / or undervolting with curve optimizer your cpu will running hot.
I own ryzen 9 5900x, it running hot like yours. But after I tweak with eco mode with PPT 88 watt, TDC 60 A, EDC 90 A, my ryzen run much cooler than before but the set back is it multicore clock reduce much. To remedy this multicore clock, I use curve optimizer -26. So now I am happy with my Ryzen 9 5900x.
I dont know if your Ryzen 3900 has feature of curve optimizer or not. But I am sure you can set eco mode.
