Hey first of all thanks for your Feedback! The Boss was actually intended but i already thought that I should have made it more obvious. My thought was that you cant kill the Death so to beat him you have to ignore him and jump over him. I didnt understand the Ghost problem. It was a Bug that came in pretty late while making the game and i tried to fix it for 3 Hours without an result.
But as I already said: thank you it really helps alot.