There is a 3D simulation I made with helixtoolkit.wpf, but it is not effective at all in terms of performance. How can I adapt this project to SharpDX? I could hardly find any information about it on the internet. Is there a resource or shortcut you can recommend?
That would be a total rewrite. HelixToolkit and SharpDX is in no way compatible in scope.
HelixTookit is a wrapper around Wpf and provides a bunch of convenient controls and functions to easily display viewports with navigation etc.
SharpDX is a wrapper around Direct3D, so provides a much lower level access to the hardware. But you would need to write a lot of components yourself to be able to provide anywhere near the level of functionality of Helix. SharpDX is also no longer maintained, so you would spend a lot of time porting to a effectively dead technology.
As always with performance you should start with profiling. Is it really Helix3D that is the bottleneck? Or are you using it in a way that is inefficient? Before doing a major rewrite you should be certain you have explored all other options for performance optimization.
One thing you might try is to export your model to a file and open it in the windows 3D viewer, I suspect that uses the same underlying wpf code to display 3D models, so it should give a fair estimation of the possible performance.