Question Not able to Raise or Lower Terrain

Hey Unity Friends,

im new here and i try to learn with tutorials. I added Terrain Tools 4.0.3 and some Assets like Trees and Grass and that stuff to build my first terrain.
Everything worked fine, but when i want Raise or Lower Terrain nothing happens when i click on that. Is there some settings i need to make that im able to "paint"? I dont know where and what.

My Unity Version is 2021.3.5f1. Maybe that Screen helps. Yes i can make a new project, but i want figure out why i can change the terrain (raise). I choose on the right Brushes and then i click on the Terrain. Before upgrade and installing Toolbox it worked..

Thanks a lot in Advance.
Alcaporzel