AMD Ryzen 9 3900 is processor manufactured by AMD and launched in Q4 2019 . It's using AM4 socket. It has 12 cores and 24 threads with clock of 3.1 GHz that can turbo clock itself to 4.3 GHz . This processor is used in Desktop devices and can consume up to 65 watts of power .
AMD Radeon RX 6900 XT is graphic card manufactured by AMD and launched in Q4 2020 . It's using PCIe 4.0 x16 bus type. It has core clock of 1825 MHz and 16384 MB (16GB) of memory . It supports DirectX 12 and OpenGL 4.6 . This graphic card is used in Desktop devices and can consume up to 300 watts of power .
This configuration has 29.6% of processor bottleneck .
When playing games your graphic card won't perform on maximum possible performances (won't be utilized to the maximum), because you processor won't process and deliver data fast enough. This theoretically means that utilization of you processor will be on maximum and the potencial of graphic card will not be completely used.
Processor bottleneck is worse, than graphic card bottleneck, because utilization of your processor will be on maximum and it will throttle other programs that are ran in background. Also you won't experience maximal performances that your graphic card offers.
You can resolve this by upgrading your processor or by downgrading your graphic card. Downgrading your graphic card doesn't make much sense and in that case is better to leave current graphic card in you computer.