Yet this does not work, what am i supposed to do?
Maybe a silly question, but did you do things like re-package it as a .pk4, with an appropriate filename etc? How certain are you that it's picking up your .map file rather than the original one?
To confirm it's using your modified map file, I'd tweak the name of one of the entities, and use "listEntities" at the console to confirm it's picked up.
I've replaced map entities at runtime through the code simply by changing the classname property, so IMO what you've described should work fine. Maybe you're accidentally changing the entity name instead? (eg it might be "weapon_shotgun_1" for the 1st one added in the map)