Second screen application UI hangs when GPU is busy with game

Question

When I start a game in Windwos 11 Pro, the UI of second screen applications hangs (Chrome - Youtube, Discord, ...) when the graphics card is busy.

What has already been done:

1. Windows 11 is up to date (and has gone through several updates over the 2 years).
2. Of course reboot (the problem has existed on the PC for 2 years).
3. I have already sought advice from several computer scientists and Windwos experts in companies, all without success (+I am a computer scientist myself).
4. The CPU and GPU were tested for functionality (the clock speeds are stable, they get as much power as they should, etc.).
5. The energy settings have been checked several times, nothing is working on efficienty mode or anything like that.
6. The Nvidia control panel was turned upside down to see if it had anything to do with it.
7. All gaming modes that are intended to focus performance solely on the game are switched off (Windows, virus software, Nvidia).
8. Changing priorities via Task Manager has no effect.
9. An attempt was made to let the motherboard's graphics card (Intel (R) UHD Graphics 770) process the UIs of the second screen applications. (This worked until a game was started and the motherboard graphics card stopped providing power.)
10. The temperature of all hardware components is within the acceptable range.
11. Event Viewer has been checked for messages that may indicate this behavior.
12. I ran sfc /scannow in CMD (run as admin) to check the system files, but that didn't fix the problem
13. All games that put a strain on the graphics card have this problem and changing the screen mode (full screen, full screen window, window) doesn't help.
14. Last but not least. Graphics card drivers are of course up to date, as are all other drivers.

Annotation:

• The logic processing of all applications works without a problem (logically, since the CPU is not used to capacity), i.e. I can talk and hear in Discord, but cannot see it (whether someone is talking or I am speaking, the display freezes), even when I get a direct message, I hear the sound, but have to tab out of the game for it to show me in Discord (the UI starts rendering again).
• Task Manager shows that the 3060 Ti is probably busy (mostly over 90% in the games), but Windows should be able to distribute minimal resources to Chrome, Discord, etc. for UI tasks and even if not, see: "What has already been done - point 9".
• Task Manager (set to always show in foreground) gets enough resources to run normally on the second screen and to show me fully that the GPU is busy. This may possibly be due to resource allocation hardcoded by Windwos (see What has already been done - point 8).
• The problem has existed since I first booted up Windows, so I don't assume that a reset will fix the problem and a BIOS update can't be the solution either.
• I was redirected here by a Microsoft agent/moderator, my original question was already posted on the Microsoft Community forum.

Conclusion:
Based on current knowledge, we assume that this is a problem with the resource distribution of Windows 11 (Pro), that when the GPU is busy, Windows is not able to distribute a few percent of performance to other applications and even worse , even other graphics cards (motherboard graphics card) cannot provide the alternative power source).

Specs:

• Windows 11 Pro
• i5 12600K (processor)
• RTX 3060 Ti (graphics card)
• B660 Gigabyte (motherboard)
• 32GB DDR4 (RAM)
• Main screen: WQHD iiyama
• Second screen: FHD Samsung
• Second Secondary screen: FHD BenQ

I'm curious to see what others here suggest, thanks for the help in advance.