Can someone tell me whet this noise in my render is?
En how can I get rid off it?
The best way is to provide the .blend file here so the users could “experiment” with Yo problem.
On the other hand this looks like reflection caustics so try to turn them OFF in the RENDER tab (Light Paths) to see the result. U could also disable refractive ones but I think there is NO refractive object in Yo scene, right? It this does NOT help the last possible step is to clamp light (direct, indirect or both - RENDER / Sampling) so try the value about 2.5 and/or filter glossy (Light Paths) and try something about 1.0.