You asked how to set hero level to 50 at map start. He perfectly answered your question.
How exactly to implement it in your map was never mentioned. If you already have a code, that does not work, then show it. (and Trigger&Scripts forum would be better place then)
If you want others to work on your map, request section is the correct place. And then you should attach your map.
But it seems that it's anyway not your map, that you edit... because you said it's in jass, and you don't seem to have knowledge about it.