Your CPU is not able to deliver enough frames for the GPU to render, so it is only partially utilized at the moment. You can either try to increase resolution and image quality details in game, which will help to move the bottleneck from the CPU to the GPU somewhat, or you need a faster CPU. The latter would be the best, albeit the more expensive option.
If you are playing lots of DX11 games, especially one that are mostly single threaded then you've made a VERY BAD CHOICE choosing AMD. AMD has notoriously bad and uneven performance in DX11 applications in heavy CPU scenarios. MOBA games like LoL can be CPU heavy.
There's nothing wrong with your CPU, and you are right in your observation -nvidia destroys even 6900XT in specific CPU heavy scenarios, because of AMD very poor DX11 driver coding, specifically API overhead.
If you can i would STRONGLY advise to return the GPU and buy 3080.
But if ill go with a 5900x or a intel 10900k i will solve the problem right ?
Because i see a lot of video of people using 6900xt and play fortnite at 200 fps 2k or LoL 400fps in 4k
Actually the RX 6900 XT does very well in DX 11 gaming if you have an up to date CPU. In addition the RX 6900 XT has 16GB of memory which means almost any resolution you wish to game at will work just fine. The RTX 3080 is a formidable GPU but good luck trying to find one to buy right now.
Yes. Go with a Ryzen 5000 series CPU to unlock the full performance of the 6900 XT. If you use a Ryzen 5000 series, you'll be able to use Smart Access Memory for further performance increases. I believe it works quite well with the Call of Duty games.
Better CPU will lessen the problem but a person with 5900x and 3080/3090 will still have better framerate in these specific CPU bound games on DX11, than a person with 5900x and 6900XT. We are obviously talking about minimum framerates, once lots of stuff appears all at once on screen, there's a lot of grass, objects, models etc. anything that causes lots of draw calls.
If you plan to play these cpu bound DX11 games and want the highest possible framerate, with much smaller FPS dips, then PLEASE BUY NVIDIA, AND RETURN YOUR AMD GPU.