Hi friends.

I have a Lenovo Legion laptop with AMD 4800H CPU, 32GB DDR4, and nVIDIA 1660 Ti 6GB VRAM, and my monitor set to 4:3 ratio. Windows 11.

I downloaded and installed the game from GOG. Everything runs normally and smoothly at maximum allowed resolution 1600 x 1200 and at highest effects.

However, once I have a lot of units on screen and on map, let's say about 10,000 units on map, and 200 units on screen in active battle. Then, I get about 1 or 2 FPS, which is very un-playable. Windows task manager shows minimal CPU GPU usage.

Should I turn down resolution, lower effects, re-install games??? Is this game open-sourced so that anyone can re-write its codes???

Thanks

Rewrite codes is not a proper solution for fixing Windows UWP mobile backported (Win8+) OS. But it is all we can do with it.
Try to find LAA fix. Uptodate version of it made for Win10/11 (this thing exist in decades and each Win since then is new problems of reintroduce old problems). PCGW. It should be some guthub link.

Go to GOG Support (if use Galaxy link at MORE section for the game in Library) game page - Additional info on PCGW. If there is fommon solutions for common issues 5hey listed there. If not on game article look to Windows article and Troubleshooting_guide page with all further links.

Try lower a bit resolution maybe? Im not familiar with modern 4:3. For widescreen displays x1200p is too high unless it is 4k display (for proper scale still better lower it).
Set everywhere Keep Aspect ratio anyway.
(reminder 1280x1024 is not 4:3)

Windows, Nvidia - both do everywhing to broke old games. Usually games up to D3D9 for Win8+ and D3D10 for NVidia are work in 1-2 fps or looks like they are 1FPS. It is normal in general.
Need 3rd party wrappers. DXVK-for-Win, WineD3D-for-Win. Em, so, general solutions for UWP Windows bad compatible with Windows NT. The only difference it is DX8 or 9 game and not DX7/earlier. So ddraw wrappers wont help.

Go to game exe properties and try change DPI scaling method to differ, as well as enable/disable Fullscreen optimisation.
As last one try Compatibility mode in addition to Disable optimisation and DPI BY APP options.

Only after go to some LAA/wrappers fixes. And when you do use them - disable Compatibility modes (DPI scaling/optimisation can stay).

UPD: Game article on PCGW have no solution. Optional tweak for refreshrate.

Disable V-sync/any *-sync everywhere incl for game itself in ini config. Use RivaTuner RTSS to limit FPS.
Close any else Overlays. UNINSTALL MSI Afterburner. And RTSS if you install them as a bundle. It is not official version of RTSS. Reinstall official one (separate).