Any idea how to fix the black borders in the settlers 3 ultimate edition (my desktop resolution is 1366x768, and i'm playing on windows 10)? I remember doing that somehow about a year ago, but i completly forgot how i did that. It's playable but still makes playing somehow difficult when you look a the border of the screen and you see black bars.
I attached image how it looks in game.
Any fix, like how to strech the game so it will fill the whole screen, or something like that.

Thank for any help.

That's because the game is in a 4:3 ratio, not 16:9. It doesn't support 16:9 because common monitors at the time (1998) were CRT "boxes", not widescreen LCDs we have today.

So there is no fix to that black borders problem?

Nope. You could only stretch the picture when you tell your graphics driver to stretch 4:3 games to the whole size of the display - but then the settlers look smaller and fatter - which imho is ugly.

If stretching is acceptable, you can change your setting in your graphics card control panel. Just change "maintain aspect ratio" to "full screen" or similar. But as adrianer said, it will look ugly.

Well i started using DxWnd and it solved the problem for me.
The game now just turns on in window mode.