With carols hints i went a step back and figured out, that AmmoJS works quite good with my terrain and i managed to get a sphere moving on it. among all i found this nice thread (especially wingnuts long comments with lots of ideas and thought enlightened me quite some time) and adopted some parts and i like that the sphere is stable moving on my ground: https://playground.babylonjs.com/#WF4P7M#42
After the sphere sliding quite hard on my terrain i thought setting mass to 0 might be a good workaround.
So my idea is on keydown mass changes to 1 and on keyup it changes back to 0, so there wont be any sliding. its working, but now i got 2 problems which i didnt manage to solve. First is when stop pressing key while sphere is meant to fall, its of course stuck up there and second, when i push two buttons and stop pressing one sphere also stops.
The First problem i thought about using the raycast after keyup and make a while loop until the sphere is on the ground. But it didnt really loop. I also tried to wait for collision after keyup and then sets the mass to 0, but then somehow the sphere was stuck. Pressing “wasd” didnt change mass back to 1.
Second Problem with the two or more buttons i tried to solve with counting pressed buttons, i expected it to count only when pushing the button, but jea it counted like every 0.1sec while pushing.
Well, if anyone has an idea would be glad to hear. I know the problem is not mesh falling through mesh anymore, but i thought if someone tries with a mesh like mine, he might end up with same problems.