Gaming PC for 4K gaming | Hardwarelux

I need your advice or help.

1. Do you want to play on PC? If yes, what?
I’d like to achieve a consistent 100fps+ at high graphics settings on my LG OLED42C27LA (3840 x 2160) in current triple AAA titles or in “graphics intensive” games.

2. Do you want to use the computer to edit photos/music/videos or similar? As a hobby or are you a professional? What software will you use?
No, the PC is used exclusively for gaming.

3. Do you have any special requirements or wishes (certain brands and manufacturers, overclocking, a particularly quiet computer, RGB lighting, …)?
It should be quiet and provide good cooling for the above purpose.
I don’t care about RGB lighting, brands, manufacturers, chassis design, or components.

4. How many screens do you want to use? Model, resolution and refresh rate (Hz)? G-Sync/FreeSync? How many FPS do you want to see?
See question 1. (I’m only using LG OLED42C27LA and don’t need any other monitors)

5. Do you still have an old computer, and some of its components can still be used?
(Please provide links or exact model names)
Specifications of my current PC – purchased from dubaro in November 2020:
Be calm! Pure Base 500DX black with glass window
AMD Ryzen 9 5900X (12x 3.7GHz / 4.8GHz Turbo)
Be calm! Dark Rock 4
MSI MPG X570 Gaming Edge WIFI (Including WiFi + BT)
32GB (2 x 16GB) GSkill DDR4 3600MHz Trident Z NEO
1000GB Kingston A2000 M.2 PCIe 3.0 x4 NVME (L 2200MB/s; S 2000MB/s)
Sasmung 980 PRO 2TB PCIe 4.0 (up to 7000MB/s) NVMe M.2 (2280)
10GB MSI RTX3080 GAMING
850W Be quiet! Dark Power Pro 11
The additional case fan is quiet! Silent wings 3 120 mm 3 pcs

I switched from my 1440p display to an LG OLED display about a month ago and I’m happy with the picture quality.
Will simply upgrading to the RTX 4090 significantly boost performance?
Unfortunately, in many games, I’m not able to reach 100fps+ and I don’t want to lower the settings too much so that the image quality suffers.
In Starfield, for example, I got 50-60 fps in cities at medium graphics settings.
I know the game is not optimized well, but I would like to get more FPS and at the same time I would like to be able to increase the graphics options in the game.
The game also seems to be quite CPU dependent – would it also make sense to upgrade the CPU to achieve more FPS? For example on Ryzen 7 7800X3D?
I would also like to be prepared for future titles so that I can fully “enjoy” the LG OLED picture quality^^

6. How much money do you want to spend?
About 3500 euros

7. When should I buy a computer?
Immediately.

8. Do you want to assemble the computer yourself or have it assembled (by the shop or by helpers (include as poster))?
Both are possible.

9. Do you want to stream your content to your computer (eg via Twitch/OBS)? If yes – what games/content? Do you already have parts for a streaming setup? (Multiple monitors, microphone, camera, streaming surface, …)?
no.

I would like to thank you in advance for any tips, advice, etc. that you can give me in this regard.