You likely have a native screen resolution above the game's supported ones.

Does the game work fine otherwise? It launches and you can play without issues?
I got some more info regarding custom settings here:
https://www.gog.com/forum/spellforce_series/spellforce_platinum_any_way_to_changeturn_off_music/post4

Well, it only works in a small window, and the monitor resolution is much higher than that supported by the game.
And Yes screen resolution is 2560 X 1440

If you open your Config.lua file in Notepad, located in the main install directory, what does it say?

Also, if you right-click on your desktop shortcut and add
-windowmode

...at the end in the Target column, you should get a larger game window, even at default resolution.

Should look like this:
[INSTALL PATH]\SpellForce.exe -windowmode

I installed the game with Gog and there is no config.lua in the folder, you need to create it, what should it contain?

How do I create a bigger window for the game?

So it's a fresh install, and you haven't been ingame yet?

Config.lua is generated automatically, but by default only contains the name of your character. It should be created when you make a character in the game.

I have never tried making a .lua file, only edited the one I already had from the game.

By default, it should look like this:
You will need to add everything else manually, aka a copy-paste, above this.
------------------------------

Stored =
{
LastPlayed = "[CHARACTER NAME]",
}
UserInterface =
{
SkipTutorial = 0,
}

------------------------------

I suggest you make a character, get ingame with the default settings, then check the Config.lua afterwards.

I entered the game, I created a character in cofnig.lua is just that. The windowed game works but I wish I could play in full screen mode normally.


Stored =
{
LastPlayed = "m",
}
UserInterface =
{
SkipTutorial = 1,
}

Sadly, that won't be possible. The game engine is so old, it was never made with widescreen support.

This should be a complete, working Config.lua for you:
Audio volume might be a bit low, but you should be able to access the ingame Audio Options with these settings.
------------------------------


UserInterface =
{
SkipTutorial = 1,
InvertZoomKey = 0,
InvertMouselook = 0,
BorderScrollSpeed = 695,
BorderScroll = 1,
RMBScroll = 0,
AutoNorth = 0,
ExtendedTooltips = 1,
GameMode = 2,
}
Graphic =
{
AvoidExcessiveFrameBuffering = 1,
VSync = 0,
FlatShades = 1,
EffectLightmap = 1,
EnvironmentMapping = 1,
AdornMode = 3,
ObjectFadeDistance = 100,
ShadowType = 3,
TextureQuality = 4,
Filtering = 4,
ScreenResolution = 4,
WindowWidth = 2560,
WindowHeight = 1440,
ShowHitInfo = 1,
}
Sound =
{
SpeakerType = 0,
Channels = 2,
VolumeSpeech = 12,
Speech = 2,
VolumeSFX = 8,
SFX = 1,
VolumeMusic = 10,
Music = 2,
}
Stored =
{
LastPlayed = "m",
}

Thanks now, I understand, it is about the monitor because I had a different one then and now I have 2k. I just don't understand why just quitting the game enters the options I never had, and the previous computer was also stronger than the requirements of the game. \
And on the previous computer, I was playing normally, not in the window. It's a pity because I liked her. But thanks for trying

This here works quite well for up to 4K if you use console commands to adjust the zoom later ingame:
https://www.moddb.com/games/spellforce-the-order-of-dawn/downloads/sf-high-resolution-mod