Maybe it's not working because of duplicated functions?

It's better not to duplicate them.

I don't understand it myself.

Well, it's better to understand. Maybe you can provide the entire script? Check the console to see what it outputs...

But here's the problem: I have issues with the editor itself. It crashes intermittently when I open the script menu.

You're lucky; it always crashed for me... Edit the scripts with Notepad or a dedicated script editor if it bothers you again.

And how do I make it so that after reading a message, a hidden hero on the map (who already has an army) teleports to me and a battle begins?

Read about the MessageBox and SetObjectPosition functions in the manual. It's not complicated.
MessageBox("path to the message", TeleporateHero);
function TeleporateHero()
SetObjectPosition("script name of the enemy hero", x coordinate, y coordinate, on the surface or in the Dungeon);
MakeHeroInteractWithObject("script name of the enemy hero", "script name of your hero");
end;

You can read more about the MessageBox and SetObjectPosition functions in the manual.