Current questions and answers regarding the map editor.

I also activated the heroes available on the map there  

When checking in the game itself, none of this works

Try adding the heroes to Academy.xdb, Dungeon_Standart.xdb, Fortress.xdb, etc. along the path MapObjects\_(AdvMapSharedGroup)\Heroes, so that they can be selected at the start and hired at the tavern.
If the map is multiplayer, you need to change <ScenarioHero>true to false in the hero files.