Intel Core i9-9900X is processor manufactured by Intel and launched in Q4 2018 . It's using FCLGA2066 socket. It has 10 cores and 20 threads with clock of 3.5 GHz that can turbo clock itself to 4.5 GHz . This processor is used in Desktop devices and can consume up to 165 watts of power .
NVIDIA GeForce GTX 1660 Ti is graphic card manufactured by NVIDIA and launched in Q1 2019 . It's using PCIe 3.0 x16 bus type. It has core clock of 1500 MHz and 6144 MB (6GB) of memory . It supports DirectX 12 and OpenGL 4.6 . This graphic card is used in Desktop devices and can consume up to 120 watts of power .
This configuration has 2.5% of processor bottleneck . Everything less than 5% should not be concerned major bottleneck.
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.